Results
- Showing results for:
- Reset all filters
Search results
-
Journal articleMatteini L, Stansby D, Horbury TS, et al., 2018,
On the 1/f spectrum in the solar wind and its connection with magnetic compressibility
, Letters of the Astrophysical Journal, Vol: 869, ISSN: 2041-8205We discuss properties of Alfvénic fluctuations with large amplitude in plasmas characterized by low magnetic field compression. We note that in such systems power laws cannot develop with arbitrarily steep slopes at large scales, i.e., when $| \delta {\boldsymbol{B}}| $ becomes of the order of the background field $| {\boldsymbol{B}}| $. In such systems there is a scale l 0 at which the spectrum has to break due to the condition of weak compressibility. A very good example of this dynamics is offered by solar wind fluctuations in Alfvénic fast streams, characterized by the property of constant field magnitude. We show here that the distribution of $\delta B=| \delta {\boldsymbol{B}}| $ in the fast wind displays a strong cutoff at $\delta B/| {\boldsymbol{B}}| \lesssim 2$, as expected for fluctuations bounded on a sphere of radius $B=| {\boldsymbol{B}}| $. This is also associated with a saturation of the rms of the fluctuations at large scales and introduces a specific length l 0, above which the amplitude of the fluctuations becomes independent on the scale l. Consistent with that, the power spectrum at l > l 0 is characterized by a −1 spectral slope, as expected for fluctuations that are scale-independent. Moreover, we show that the spectral break between the 1/f and inertial range in solar wind spectra indeed corresponds to the scale l 0 at which $\langle \delta B/B\rangle \sim 1$. Such a simple model provides a possible alternative explanation of magnetic spectra observed in interplanetary space, also pointing out the inconsistency for a plasma to simultaneously maintain $| {\boldsymbol{B}}| \sim \mathrm{const}.$ at arbitrarily large scales and satisfy a Kolmogorov scaling.
-
Journal articleGuo RL, Yao ZH, Sergis N, et al., 2018,
Reconnection Acceleration in Saturn's Dayside Magnetodisk: A Multicase Study with Cassini
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 868, ISSN: 2041-8205 -
Journal articleHesse M, Norgren C, Tenfjord P, et al., 2018,
On the role of separatrix instabilities in heating the reconnection outflow region
, Physics of Plasmas, Vol: 25, ISSN: 1070-664XA study of the role microinstabilities at the reconnection separatrix can play in heating the electrons during the transition from inflow to outflow is being presented. We find that very strong flow shears at the separatrix layer lead to counterstreaming electron distributions in the region around the separatrix, which become unstable to a beam-type instability. Similar to what has been seen in earlier research, the ensuing instability leads to the formation of propagating electrostatic solitons. We show here that this region of strong electrostatic turbulence is the predominant electron heating site when transiting from inflow to outflow. The heating is the result of heating generated by electrostatic turbulence driven by overlapping beams, and its macroscopic effect is a quasi-viscous contribution to the overall electron energy balance. We suggest that instabilities at the separatrix can play a key role in the overall electron energy balance in magnetic reconnection.
-
Journal articleHattermann FF, Wortmann M, Liersch S, et al., 2018,
Simulation of flood hazard and risk in the Danube basin with the Future Danube Model
, Climate Services, Vol: 12, Pages: 14-26, ISSN: 2405-8807Major river and flash flood events have accumulated in Central and Eastern Europe over the last decade reminding the public as well as the insurance sector that climate related risks are likely to become even more damaging and prevalent as climate patterns change. However, information about current and future hydro-climatic extremes is often not available. The Future Danube Model (FDM) is an end-user driven multi-hazard and risk model suite for the Danube region that has been developed to provide climate services related to perils such as heavy precipitation, heat waves, floods, and droughts under recent and scenario conditions. As a result, it provides spatially consistent information on extreme events and natural resources throughout the entire Danube catchment. It can be used to quantify climate risks, to support the implementation of the EU framework directives, for climate informed urban and land use planning, water resources management, and for climate proofing of large scale infrastructural planning including cost benefit analysis. The model suite consists of five individual and exchangeable modules: a weather and climate module, a hydrological module, a risk module, an adaptation module, and a web-based visualization module. They are linked in such a way that output from one module can either be used standalone or fed into subsequent modules. The utility of the tool has been tested by experts and stakeholders. The results show that more and more intense hydrological extremes are likely to occur under climate scenario conditions, e.g. higher order floods may occur more frequently.
-
Journal articleRichardson TB, Forster PM, Andrews T, et al., 2018,
Drivers of Precipitation Change: An Energetic Understanding
, Journal of Climate, Vol: 31, Pages: 9641-9657, ISSN: 0894-8755The response of the hydrological cycle to climate forcings can be understood within the atmospheric energy budget framework. In this study precipitation and energy budget responses to five forcing agents are analyzed using 10 climate models from the Precipitation Driver Response Model Intercomparison Project (PDRMIP). Precipitation changes are split into a forcing-dependent fast response and a temperature-driven hydrological sensitivity. Globally, when normalized by top-of-atmosphere (TOA) forcing, fast precipitation changes are most sensitive to strongly absorbing drivers (CO2, black carbon). However, over land fast precipitation changes are most sensitive to weakly absorbing drivers (sulfate, solar) and are linked to rapid circulation changes. Despite this, land-mean fast responses to CO2 and black carbon exhibit more intermodel spread. Globally, the hydrological sensitivity is consistent across forcings, mainly associated with increased longwave cooling, which is highly correlated with intermodel spread. The land-mean hydrological sensitivity is weaker, consistent with limited moisture availability. The PDRMIP results are used to construct a simple model for land-mean and sea-mean precipitation change based on sea surface temperature change and TOA forcing. The model matches well with CMIP5 ensemble mean historical and future projections, and is used to understand the contributions of different drivers. During the twentieth century, temperature-driven intensification of land-mean precipitation has been masked by fast precipitation responses to anthropogenic sulfate and volcanic forcing, consistent with the small observed trend. However, as projected sulfate forcing decreases, and warming continues, land-mean precipitation is expected to increase more rapidly, and may become clearly observable by the mid-twenty-first century.
-
Journal articleEggington J, Mejnertsen L, Desai R, et al., 2018,
Forging links in Earth's plasma environment
, Astronomy and Geophysics, Vol: 59, Pages: 6.26-6.28, ISSN: 1366-8781 -
Journal articleJohlander A, Vaivads A, Khotyaintsev YV, et al., 2018,
Shock ripples observed by the MMS spacecraft: ion reflection and dispersive properties
, PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 60, ISSN: 0741-3335- Author Web Link
- Cite
- Citations: 21
-
Journal articleKrupp N, Roussos E, Kollmann P, et al., 2018,
Energetic Neutral and Charged Particle Measurements in the Inner Saturnian Magnetosphere During the Grand Finale Orbits of Cassini 2016/2017
, GEOPHYSICAL RESEARCH LETTERS, Vol: 45, Pages: 10847-10854, ISSN: 0094-8276 -
Book chapterDougherty M, Buratti BJ, Seidelmann PK, et al., 2018,
Enceladus as an active world: History and discovery. In Enceladus and the Icy
, Enceladus and the Icy Moons of Saturn, Editors: Schenk, Clark, Howett, Verbiscer, Waite, Publisher: University of Arizona Press, Pages: 3-16, ISBN: 9780816537075Dougherty M. K., Buratti B. J., Seidelmann P. K., and Spencer J. R. (2018) Enceladus as an active world: History and discovery. In Enceladus and the Icy Moons of Saturn (P. M. Schenk et al., eds.), pp. 3–16. Univ. of Arizona, Tucson, DOI: ...
-
Journal articleInai Y, Fujita R, Machida T, et al., 2018,
Seasonal characteristics of chemical and dynamical transports into the extratropical upper troposphere/lower stratosphere
<jats:p>Abstract. To investigate the seasonal characteristics of chemical tracer distributions in the extratropical upper troposphere and lower stratosphere (ExUTLS) as well as stratosphere–troposphere exchange processes, mixing fractions of air masses originating in the stratosphere, tropical troposphere, mid-latitude lower troposphere (LT), and high-latitude LT in the ExUTLS are estimated using 90-day backward trajectories calculated with European Centre For Medium-Range Weather Forecasts (ECMWF) ERA-Interim data as the meteorological input. Time-series of chemical tracers obtained from ground-based and airborne observations are incorporated into the estimated mixing fractions, thus reconstructing spatiotemporal distributions of chemical tracers in the ExUTLS. The reconstructed tracer distributions are analysed with the mixing fractions and the stratospheric age of air (AoA) estimated using a 10-year backward trajectory. The reconstructed distributions of CO and CO2 in the ExUTLS are affected primarily by tropospheric air masses because of the short chemical lifetime of the former and large seasonal variations in the troposphere of the latter. Distributions of CH4, N2O, and SF6 are controlled primarily by seasonally varying air masses transported from the stratosphere. For CH4 and N2O distributions, air masses transported via the deep branch of the Brewer–Dobson circulation are particularly important. This interpretation is qualitatively and quantitatively supported by the estimated spatiotemporal distributions of AoA. </jats:p>
-
Journal articleStansby D, Salem C, Matteini L, et al., 2018,
A new inner heliosphere proton parameter dataset from the Helios mission
, Solar Physics, Vol: 293, ISSN: 0038-0938In the near future, Parker Solar Probe and Solar Orbiter will provide the first comprehensive in-situ measurements of the solar wind in the inner heliosphere since the Helios mission in the 1970s. We describe a reprocessing of the original Helios ion distribution functions to provide reliable and reproducible data to characterise the proton core population of the solar wind in the inner heliosphere. A systematic fitting of bi-Maxwellian distribution functions was performed to the raw Helios ion distribution function data to extract the proton core number density, velocity, and temperatures parallel and perpendicular to the magnetic field. We present radial trends of these derived proton parameters, forming a benchmark to which new measurements in the inner heliosphere will be compared. The new dataset has been made openly available for other researchers to use, along with the source code used to generate it.
-
Journal articleSorba AM, Achilleos NA, Guio P, et al., 2018,
The Periodic Flapping and Breathing of Saturn's Magnetodisk During Equinox
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 123, Pages: 8292-8316, ISSN: 2169-9380 -
Journal articleHwang KJ, Sibeck DG, Burch JL, et al., 2018,
Small-scale flux transfer events formed in the reconnection exhaust region between two X lines
, Journal of Geophysical Research: Space Physics, Vol: 123, Pages: 8473-8488, ISSN: 2169-9380We report MMS observations of the ion-scale flux transfer events (FTEs) that may involve two main X lines and tearing instability between the two X lines. The four spacecraft detected multiple isolated regions with enhanced magnetic field strength and bipolar Bn signatures normal to the nominal magnetopause, indicating FTEs. The currents within the FTEs flow mostly parallel to B, and the magnetic tension force is balanced by the total pressure gradient force. During these events, the plasma bulk flow velocity was directed southward. Detailed analysis of the magnetic and electric field and plasma moments variations suggests that the FTEs were initially embedded within the exhaust region north of an X line but were later located southward/downstream of a subsequent X line. The cross sections of the individual FTEs are in the range of ~2.5–6.8 ion inertial lengths. The observations suggest the formation of multiple secondary FTEs. The presence of an X line in the exhaust region southward of a second X line results from the southward drift of an old X line and the reformation of a new X line. The current layer between the two X lines is unstable to the tearing instability, generating multiple ion-scale flux-rope-type secondary islands.
-
Journal articleYao ZH, Radioti A, Grodent D, et al., 2018,
Recurrent Magnetic Dipolarization at Saturn: Revealed by Cassini
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 123, Pages: 8502-8517, ISSN: 2169-9380 -
Journal articleTong Y, Vasko I, Mozer FS, et al., 2018,
Simultaneous Multispacecraft Probing of Electron Phase Space Holes
, GEOPHYSICAL RESEARCH LETTERS, Vol: 45, Pages: 11513-11519, ISSN: 0094-8276- Author Web Link
- Cite
- Citations: 31
-
Journal articleSmith CJ, Kramer RJ, Myhre G, et al., 2018,
Understanding rapid adjustments to diverse forcing agents
, Geophysical Research Letters, Vol: 45, Pages: 12023-12031, ISSN: 0094-8276Rapid adjustments are responses to forcing agents that cause a perturbation to the top of atmosphere energy budget but are uncoupled to changes in surface warming. Different mechanisms are responsible for these adjustments for a variety of climate drivers. These remain to be quantified in detail. It is shown that rapid adjustments reduce the effective radiative forcing (ERF) of black carbon by half of the instantaneous forcing, but for CO2 forcing, rapid adjustments increase ERF. Competing tropospheric adjustments for CO2 forcing are individually significant but sum to zero, such that the ERF equals the stratospherically adjusted radiative forcing, but this is not true for other forcing agents. Additional experiments of increase in the solar constant and increase in CH4 are used to show that a key factor of the rapid adjustment for an individual climate driver is changes in temperature in the upper troposphere and lower stratosphere.
-
Journal articleSchwartz SJ, Avanov L, Turner D, et al., 2018,
Ion kinetics in a hot flow anomaly: MMS observations
, Geophysical Research Letters, Vol: 45, Pages: 11520-11529, ISSN: 0094-8276Hot Flow Anomalies (HFAs) are transients observed at planetary bow shocks, formed by the shock interaction with a convected interplanetary current sheet. The primary interpretation relies on reflected ions channeled upstream along the current sheet. The short duration of HFAs has made direct observations of this process difficult. We employ high resolution measurements by NASA's Magnetospheric Multiscale Mission to probe the ion microphysics within a HFA. Magnetospheric Multiscale Mission data reveal a smoothly varying internal density and pressure, which increase toward the trailing edge of the HFA, sweeping up particles trapped within the current sheet. We find remnants of reflected or other backstreaming ions traveling along the current sheet, but most of these are not fast enough to out-run the incident current sheet convection. Despite the high level of internal turbulence, incident and backstreaming ions appear to couple gyro-kinetically in a coherent manner.
-
Journal articleVasquez BJ, Forman MA, Coburn JT, et al., 2018,
The Turbulent Cascade for High Cross-helicity States at 1 au. II. Minor Energy
, ASTROPHYSICAL JOURNAL, Vol: 867, ISSN: 0004-637X -
Journal articleTinetti G, Drossart P, Eccleston P, et al., 2018,
A chemical survey of exoplanets with ARIEL
, Experimental Astronomy, Vol: 46, Pages: 135-209, ISSN: 0922-6435Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet’s birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25–7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using know
-
Journal articleWeiss Z, Pickering JC, Hoffmann V, 2018,
Obituary Prof. Edward B. M. Steers (1931-2018)
, SPECTROCHIMICA ACTA PART B-ATOMIC SPECTROSCOPY, Vol: 149, Pages: 241-242, ISSN: 0584-8547 -
Journal articleHajra R, Henri P, Myllys M, et al., 2018,
Cometary plasma response to interplanetary corotating interaction regions during 2016 June-September: a quantitative study by the Rosetta Plasma Consortium
, Monthly Notices of the Royal Astronomical Society, Vol: 480, Pages: 4544-4556, ISSN: 0035-8711Four interplanetary corotating interaction regions (CIRs) were identified during 2016 June–September by the Rosetta Plasma Consortium (RPC) monitoring in situ the plasma environment of the comet 67P/Churyumov–Gerasimenko (67P) at heliocentric distances of ∼3–3.8 au. The CIRs, formed in the interface region between low- and high-speed solar wind streams with speeds of ∼320–400 km s−1 and ∼580–640 km s−1, respectively, are characterized by relative increases in solar wind proton density by factors of ∼13–29, in proton temperature by ∼7–29, and in magnetic field by ∼1–4 with respect to the pre-CIR values. The CIR boundaries are well defined with interplanetary discontinuities. Out of 10 discontinuities, four are determined to be forward waves and five are reverse waves, propagating at ∼5–92 per cent of the magnetosonic speed at angles of ∼20°–87° relative to ambient magnetic field. Only one is identified to be a quasi-parallel forward shock with magnetosonic Mach number of ∼1.48 and shock normal angle of ∼41°. The cometary ionosphere response was monitored by Rosetta from cometocentric distances of ∼4–30 km. A quiet time plasma density map was developed by considering dependences on cometary latitude, longitude, and cometocentric distance of Rosetta observations before and after each of the CIR intervals. The CIRs lead to plasma density enhancements of ∼500–1000 per cent with respect to the quiet time reference level. Ionospheric modelling shows that increased ionization rate due to enhanced ionizing (>12–200 eV) electron impact is the prime cause of the large cometary plasma density enhancements during the CIRs. Plausible origin mechanisms of the cometary ionizing electron enhancements are discussed.
-
Journal articleArcher MO, Hartinger MD, Redmon R, et al., 2018,
First results from sonification and exploratory cttizen science of magnetospheric ULF waves: long-lasting decreasing-frequency poloidal Field line resonance following geomagnetic storms
, Space Weather, Vol: 16, Pages: 1753-1769, ISSN: 1539-4956Magnetospheric ultralow‐frequency (ULF) waves contribute to space weather in the solar wind‐magnetosphere‐ionosphere system. The monitoring of these waves by space‐ and ground‐based instruments, however, produces big data, which are difficult to navigate, mine, and analyze effectively. We present sonification, the process of converting an oscillatory time series into audible sound, and citizen science, where members of the public contribute to scientific investigations, as a means to potentially help tackle these issues. Magnetometer data in the ULF range at geostationary orbit have been sonified and released to London high schools as part of exploratory projects. While this approach reduces the overall likelihood of useful results from any particular group of citizen scientists compared to typical citizen science projects, it promotes independent learning and problem solving by all participants and can result in a small number of unexpected research outcomes. We present one such example, a case study identified by a group of students of decreasing‐frequency poloidal field line resonances over multiple days found to occur during the recovery phase of a coronal mass ejection‐driven geomagnetic storm. Simultaneous plasma density measurements show that the decreasing frequencies were due to the refilling of the plasmasphere following the storm. The waves were likely generated by internal plasma processes. Further exploration of the audio revealed many similar events following other major storms; thus, they are much more common than previously thought. We therefore highlight the potential of sonification and exploratory citizen science in addressing some of the challenges facing ULF wave research.
-
Journal articleLiu F, Wienke C, Fiencke C, et al., 2018,
Biofilter with mixture of pine bark and expanded clay as packing material for methane treatment in lab-scale experiment and field-scale implementation
, Environmental Science and Pollution Research, Vol: 25, Pages: 31297-31306, ISSN: 0944-1344 -
Journal articleGoodrich KA, Ergun R, Schwartz SJ, et al., 2018,
MMS Observations of Electrostatic Waves in an Oblique Shock Crossing
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 123, Pages: 9430-9442, ISSN: 2169-9380- Author Web Link
- Cite
- Citations: 53
-
Journal articleMyhre G, Kramer RJ, Smith CJ, et al., 2018,
Quantifying the importance of rapid adjustments for global precipitation changes
, Geophysical Research Letters, Vol: 20, Pages: 11399-11405, ISSN: 0094-8276Different climate drivers influence precipitation in different ways. Here we use radiative kernels to understand the influence of rapid adjustment processes on precipitation in climate models. Rapid adjustments are generally triggered by the initial heating or cooling of the atmosphere from an external climate driver. For precipitation changes, rapid adjustments due to changes in temperature, water vapor, and clouds are most important. In this study we have investigated five climate drivers (CO2, CH4, solar irradiance, black carbon, and sulfate aerosols). The fast precipitation responses to a doubling of CO2 and a 10-fold increase in black carbon are found to be similar, despite very different instantaneous changes in the radiative cooling, individual rapid adjustments, and sensible heating. The model diversity in rapid adjustments is smaller for the experiment involving an increase in the solar irradiance compared to the other climate driver perturbations, and this is also seen in the precipitation changes.
-
Journal articleShawki D, Voulgarakis A, Chakraborty A, et al., 2018,
The South Asian monsoon response to remote aerosols: global and regional mechanisms
, Journal of Geophysical Research, Vol: 123, Pages: 11585-11601, ISSN: 0148-0227The South Asian summer monsoon has been suggested to be influenced by atmospheric aerosols, and this influence can be the result of either local or remote emissions. We have used the Hadley Centre Global Environment Model Version 3 (HadGEM3) coupled atmosphere‐ocean climate model to investigate for the first time the centennial‐scale South Asian precipitation response to emissions of sulfur dioxide (SO2), the dominant anthropogenic precursor of sulfate aerosol, from different midlatitude regions. Despite the localized nature of the regional heating that results from removing SO2 emissions, all experiments featured a similar large‐scale precipitation response over South Asia, driven by ocean‐modulated changes in the net cross‐equatorial heat transport and an opposing cross‐equatorial northward moisture transport. The effects are linearly additive, with the sum of the responses from the experiments where SO2 is removed from the United States, Europe, and East Asia resembling the response seen in the experiment where emissions are removed from the northern midlatitudes as a whole, but with East Asia being the largest contributor, even per unit of emission or top‐of‐atmosphere radiative forcing. This stems from the fact that East Asian emissions can more easily influence regional land‐sea thermal contrasts and sea level pressure differences that drive the monsoon circulation, compared to emissions from more remote regions. Our results suggest that radiative effects of remote pollution should not be neglected when examining changes in South Asian climate and that and it is important to examine such effects in coupled ocean‐atmosphere modeling frameworks.
-
Conference paperSmith CW, Coburn JT, Vasquez BJ, et al., 2018,
Correlation Scales of the Turbulent Cascade at 1 AU
, 17th Annual International Astrophysics Conference (AIAC) on Dissipative and Heating Processes in Collisionless Plasma - The Solar Corona, The Solar Wind, and The Interstellar Medium, Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588 -
Journal articleBandyopadhyay R, Chasapis A, Chhiber R, et al., 2018,
Solar Wind Turbulence Studies Using MMS Fast Plasma Investigation Data
, ASTROPHYSICAL JOURNAL, Vol: 866, ISSN: 0004-637X- Author Web Link
- Cite
- Citations: 44
-
Journal articleKhurana KK, Dougherty MK, Provan G, et al., 2018,
Discovery of atmospheric-wind-driven electric currents in Saturn's magnetosphere in the gap between Saturn and its rings
, Geophysical Research Letters, Vol: 45, Pages: 10068-10074, ISSN: 0094-8276Magnetic field observations obtained by the Cassini spacecraft as it traversed regions inside of Saturn's D ring packed a genuine surprise. The azimuthal component of the magnetic field recorded a consistent positive perturbation with a strength of 15–25 nT near closest approach. The closest approaches were near the equatorial plane of Saturn and were distributed narrowly around local noon and brought the spacecraft to within 2,550 km of Saturn's cloud tops. Modeling of this perturbation shows that it is not of internal origin but is produced by external currents that couple the low‐latitude northern ionosphere to the low‐latitude southern ionosphere. The azimuthal perturbations diminish at higher latitudes on field lines that connect to Saturn's icy rings. The sense of the current system suggests that the southern feet of the field lines in the ionosphere leads their northern counterparts. We show that the observed field perturbations are consistent with a field‐aligned current whose strength is ~1 MA/radian, that is, comparable in strength to the planetary‐period‐oscillation‐related current systems observed in the auroral zone. We show that the Lorentz force in the ionosphere extracts momentum from the faster moving low‐latitude zonal belt and delivers it to the northern ionosphere. We further show that the electric current is generated when the two ends of a field line are embedded in zonal flows with differing wind speeds in the low‐latitude thermosphere. The wind‐generated currents dissipate 2 × 1011W of thermal power, similar to the input from the solar extreme ultraviolet flux in this region.
-
Journal articleHanna E, Fettweis X, Hall RJ, 2018,
Brief communication: Recent changes in summer Greenland blocking captured by none of the CMIP5 models
, CRYOSPHERE, Vol: 12, Pages: 3287-3292, ISSN: 1994-0416- Author Web Link
- Cite
- Citations: 56
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.