The Predictive Capabilities of the Auroral Electrojet Index for Medium Energy Electron Precipitation

The chemical imprint of the energetic electron precipitation on the atmosphere is now acknowledged as a part of the natural forcing of the climate system. It has, however, been questioned to which degree current proxies are able to quantify the medium energy electron (MEE) (≳30 keV) precipitation and the associated daily and decadal variability. It is particularly challenging to model the high energy tail (≳300 keV) of MEE, both in terms of the intensity as well as the timing. This study explores the predictive capabilities of the AE index for the MEE precipitation. MEE measurements from the NOAA/POES over a full solar cycle from 2004 to 2014 are applied. We combine observations from the MEPED 0° and 90° detectors together with theory of pitch angle diffusion by wave-particle interaction to estimate the precipitating fluxes. To explore the energy dependent time scales, each of the MEPED energy channels, > 43, >114, and >292 keV are evaluated independently. While there is a strong correlation between the daily resolved AE index and >43 keV fluxes, it is a poor predictor for the >292 keV fluxes. We create new AE based MEE proxies by accumulating the AE activity over multiple days, including terms counting for the associated lifetimes. The results indicate that AE based proxies can predict at least 70% of the observed MEE precipitation variance at all energies. The potential link between the AE index, substorms and the MEE precipitation is discussed.

Sign-Singularity Analysis of Field-Aligned Currents in the Ionosphere

Field-aligned currents (FACs) flowing in the auroral ionosphere are a complex system of upward and downward currents, which play a fundamental role in the magnetosphere–ionosphere coupling and in the ionospheric heating. Here, using data from the ESA-Swarm multi-satellite mission, we studied the complex structure of FACs by investigating sign-singularity scaling features for two different conditions of a high-latitude substorm activity level as monitored by the AE index. The results clearly showed the sign-singular character of FACs supporting the complex and filamentary nature of these currents. Furthermore, we found evidence of the occurrence of a topological change of these current systems, which was accompanied by a change of the scaling features at spatial scales larger than 30 km. This change was interpreted in terms of a sort of symmetry-breaking phenomenon due to a dynamical topological transition of the FAC structure as a consequence of FACs and substorm current wedge intensification during substorms.

Multiscale analysis of a current sheet embedded in a fast earthward flow during a substorm event detected by MMS

<p>In July 2017, the MMS constellation was evolving in the magnetotail with an apogee of 25 Earth radii and an average inter-satellite distance of 10 km (i.e. at electron scales). On 23 rd of July around 16:19 UT, MMS was located at the edge of the current sheet which was in a quasi-static state. Then, MMS<br>suddenly entered in the central plasma sheet and detected the local onset of a small substorm as indicated by the AE index (~400 nT). Fast earthward plasma flows were measured for about 1 hour starting with a period of quasi-steady flow and followed by a saw-tooth like series of plasma jets (“bursty bulk flows”). In the present study, we focus on a short sequence related to an ion scale current sheet crossing embedded in a fast earthward flow. We analyse in detail two other kinetic structures in the vicinity of this current sheet: an ion-scale flux rope and an electron vortex magnetic hole and discuss the Ohm’s law and conversion energy processes.</p>

Study on the associative effects of different proportions of soybean pod, alfalfa and concentrate on the diets at different ratio of concentrate to roughage in vitro

This study aimed to determine the associative effects (AEs) of 28 feed combinations of concentrate/soybean pod/alfalfa at different concentrate-roughage ratios that were incubated for 72 h in single tubes (120 ml) which were added 30 ml rumen buffered fluid. The gas production (GP) at 0, 2, 4, 6, 9, 12, 24, 36, 48, 72 h was recorded. A single exponential equation was applied to calculate the GP parameters a (rapid GP), b (slow GP), a + b (GP potential) and c (rate constant of slow GP that can reflect the specific process of GP, rapid and slow GP and GP rate). The AEs were calculated by 72 h GP and weighted estimation value of each combination. After 72 h incubation, pH, volatile fatty acids (VFA) and ammonia nitrogen (NH₃–N), dry matter digestibility (DMD), organic matter digestibility (OMD) were determined the incubation fluid and residues. The single-factor AE index (SFAEI) and multiple-factor AE index (MFAEI) were computed. The results showed that the groups 50 : 50 : 0, 40 : 60 : 0, 60 : 20 : 20, 60 : 10 : 30, 50 : 30 : 20, 50 : 20 : 30, 40 : 50 : 10, 30 : 55 : 15, 30 : 40 : 30, 20 : 65 : 15, 20 : 50 : 30 had higher GP_{72 h}, a, b, DMD, OMD, NH₃–N, in addition, higher AE of GP, DMD, OMD, total VFA and NH₃–N than those of the other groups (P < 0.05 or P < 0.01), especially the group 30 : 55 : 15 was optimal. In conclusion, in vitro data reveal reliable fermentability and the highest SFAEI and MFAEI occurred when concentrate, soybean pod and alfalfa were combined at the ratios of 50 : 50 : 0, 40 : 60 : 0, 60 : 20 : 20, 60 : 10 : 30, 50 : 30 : 20, 50 : 20 : 30, 40 : 50 : 10, 30 : 55 : 15, 30 : 40 : 30, 20 : 65 : 15, 20 : 50 : 30.

Statistical properties of ions in bursty bulk flows

<p>With the observations of THEMIS and MMS Mission, we have investigated the properties of ions in bursty bulk flows (BBFs). Based on analysis of 315 BBF events, we can obtain the statistical features of ions in the BBFs. The results can be summarized as follows: (1) the occurrence rate of BBFs is related with AE index, which is also confirmed by previous studies; (2) the ion number density in the duskside is nearly at the same level with that in the dawnside; (3) in the region -10<em>R<sub>E</sub></em> > <em>X<sub>GSM</sub></em>> -15<em>R<sub>E</sub></em>(where <em>R<sub>E</sub></em>is the earth radius), the ion temperature in the duskside is much higher than that in the dawnside; (4) the ion temperature anisotropy <em>T</em><sub>⊥</sub>/<em>T</em><sub>∥ </sub>is weaker as BBFs close to the Earth; (5) corresponds to cold electrons (<em>T<sub>e</sub></em> < 1.5 keV), the ratio of the ion and electron temperature <em>T</em><sub>i</sub>/<em>T</em><sub>e</sub> can reach 10-15 and the temperature of ions and electrons have a linear correlation.</p>

Analysis of energy conversion processes at kinetic scales associated with a series of dipolarization fronts observed by MMS during a substorm

<p>In July 2017, the MMS constellation was in the magnetotail with an apogee of 25 Earth radii<br>and an average inter-satellite distance of 10 km (i.e. at electron scales). On 23 July around<br>16:19 UT, MMS was located at the edge of the current sheet which was in a quasi-static<br>state. Then, MMS suddenly entered in the central plasma sheet and detected the local onset<br>of a small substorm as indicated by the AE index (~400 nT). Fast earthward plasma flows<br>were measured for about 1 hour starting with a period of quasi-steady flow and followed by<br>a saw-tooth like series of fast flows associated with dipolarization fronts. This plasma<br>transport sequence finished with a flow reversal still occurring close to the magnetic<br>equator. In the present study, we investigate the energy conversion processes at ion and<br>electron scales for these different phases with particular attention on the processes in the<br>vicinity of the dipolarization fronts.</p>

Newly Formed Energy Dispersion Signatures of Low-energy Proton, Oxygen and Helium Ions in the Inner Magnetosphere

<p>Here we report the observations of the simultaneously formed energy dispersion structures of proton, oxygen and helium ions in the inner magnetospehre using Van Allen Probes data. The energy of the ourter edge of this sturcture is only several eV, and the energy of this structure is increasing with the decreasing L shell, which can be up to several keV especially for oxygen ions. The energy dispersion structure has a larger upper energy limit for the particle species with largher mass. But the upper velocity limits for different ion species are almost the same, which indicates that these different ions are accelerated by electric fields via the <strong>E</strong>x<strong>B </strong>drift. A statistical study with four years data shows that 1. This kind of structure is mainly distributed in the duskside and nighside; 2. The upper velocity for the oxygen ion exhibits a linear relation with both proton and helium ions; 3. The relationship between the occurrence rates and different parameters such as solar wind velocity, solar wind pressure, SYMH, Kp and AE index indicates that the formation of this structure is probably related to substorm activities.</p>