scholarly journals Magnetic local time asymmetries in precipitating electron and proton populations with and without substorm activity

2019 ◽  
Vol 37 (6) ◽  
pp. 1063-1077 ◽  
Author(s):  
Olesya Yakovchuk ◽  
Jan Maik Wissing
Keyword(s):  
Local Time ◽  
Flux Distribution ◽  
High Energy ◽  
Auroral Oval ◽  
Geomagnetic Disturbance ◽  
Particle Energy ◽  
Magnetic Local Time ◽  
Energy Bands ◽  
Cusp Region ◽  
Substorm Activity

Abstract. The magnetic local time (MLT) dependence of electron (0.15–300 keV) and proton (0.15–6900 keV) precipitation into the atmosphere based on National Oceanic and Atmospheric Administration POES and METOP satellite data during 2001–2008 was described. Using modified APEX coordinates the influence of particle energy, substorm activity and geomagnetic disturbance on the MLT flux distribution was statistically analysed. Some of the findings are the following. a. Substorms mostly increase particle precipitation in the night sector by about factor 2–4, but can also reduce it in the day sector.b. MLT dependence can be assigned to particles entering the magnetosphere at the cusp region and magnetospheric particles in combination with energy-specific drifts (in agreement with Newell et al., 2009).c. MLT flux differences of up to 2 orders of magnitude have been identified inside the auroral oval during geomagnetically disturbed conditions. The novelty here is the comprehensive coverage of energy bands and the focus on asymmetry.d. The maximum flux asymmetry ratio depends on particle energy, decreasing with Kp for low energetic particles and increasing with Kp for higher energy electrons, while high energy protons show a more complex dependency. While some aspects may already have been known, the quantification of the flux asymmetry sheds new light on MLT variation.

scholarly journals Magnetic local time asymmetries in electron and proton precipitation with and without substorm activity

2019 ◽  
Author(s):  
Olesya Yakovchuk ◽  
Jan Maik Wissing
Keyword(s):  
Local Time ◽  
Particle Flux ◽  
Flux Distribution ◽  
Auroral Oval ◽  
Geomagnetic Disturbance ◽  
Particle Energy ◽  
Magnetic Local Time ◽  
Asymmetry Ratio ◽  
Substorm Activity ◽  
Proton Precipitation

Abstract. The magnetic local time (MLT) dependence of electron (0.15–300 keV) and proton (0.15–6900 keV) precipitation into the atmosphere based on National Oceanic and Atmospheric Administration POES and METOP satellites data during 2001–2008 was described. Using modified APEX coordinates the influence of particle energy, substorm activity and geomagnetic disturbance on the MLT flux distribution was statistically analysed. Some of the findings are: a) MLT flux differences of up to 1 : 25 have been localized inside the auroral oval. b) MLT dependence can be assigned to different particle sources and energy-specific drifts. c) The maximum flux asymmetry ratio depends on particle energy, but not necessarily on geomagnetic disturbance. For protons it is invariant with Kp, for electrons the dependence varies with Kp and kinetic energy defines how. d) Substorms mostly increase particle precipitation in the night-sector by about factor 2–4 but can also reduce it in the day-sector. Finally we have a look at MLT-dependent trapped particle flux in the plasmasphere, which shows vast and abstract MLT differences.

scholarly journals Comparison of the magnetic equivalent convection direction and ionospheric convection observed by the SuperDARN radars

2006 ◽  
Vol 24 (11) ◽  
pp. 2981-2990 ◽  
Author(s):  
L. V. Benkevitch ◽  
A. V. Koustov ◽  
J. Liang ◽  
J. F. Watermann
Keyword(s):  
Local Time ◽  
High Latitude ◽  
Early Morning ◽  
Auroral Oval ◽  
Magnetic Local Time ◽  
Ionospheric Convection ◽  
Morning Sector ◽  
Magnetometer Data ◽  
Different Seasons

Abstract. SuperDARN radar and high-latitude magnetometer observations are used to statistically investigate quality of the convection direction estimates from magnetometer data if assumption is made that the magnetic equivalent convection vector (MEC) corresponds to the convection direction. The statistics includes five full days, ~75 000 of joint individual measurements for different seasons. It is demonstrated that the best (worst) agreement between the MEC and ionospheric convection occurs for the sunlit, summer (dark, winter) ionosphere. Overall, the MEC direction is reasonable (deviates less than 45° from the SuperDARN direction) in at least ~55% of points and it is better for the latitudes of the auroral oval. In terms of the magnetic local time, the agreement is the best (worst) in the dusk (early morning) sector. Possible reasons for differences between the MEC and ionospheric convection directions are discussed.

Dynamics of the postnoon auroral oval

1986 ◽  
Vol 64 (10) ◽  
pp. 1432-1436
Author(s):  
D. J. McEwen ◽  
F. Creutzberg
Keyword(s):  
Boundary Layer ◽  
Local Time ◽  
Auroral Oval ◽  
Magnetic Local Time ◽  
Optical Observations ◽  
Particle Detectors ◽  
Time Period ◽  
Local Injections ◽  
East West ◽  
Precipitation Events

The morphology of the postnoon auroral oval (1300–1500 magnetic local time) as determined by ground-based optical observations with all-sky TV's and meridian scanners at Sachs Harbour, N.W.T., and Cape Parry, N.W.T., is described. Arcs associated with the "inverted-V" type of precipitation events, frequently observed with rocket and spacecraft particle detectors during this time period, are found to be short-lived, narrow, and sometimes of very restricted east–west extent. These arcs form the main feature of the auroral oval, which appears to be delineated almost ex0clusively by 6300-Å emission. The mechanism for their generation is consistent with local injections of magnetosheath plasma into the dayside boundary layer.

scholarly journals Surveying pulsating auroras

2020 ◽  
Vol 38 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Eric Grono ◽  
Eric Donovan
Keyword(s):  
Local Time ◽  
Equatorial Plane ◽  
Early Morning ◽  
Auroral Oval ◽  
Magnetic Local Time ◽  
Occurrence Probability ◽  
Inner Magnetosphere ◽  
Magnetic Latitude ◽  
Source Regions ◽  
Proton Aurora

Abstract. The early-morning auroral oval is dominated by pulsating auroras. These auroras have often been discussed as if they are one phenomenon, but they are not. Pulsating auroras are separable based on the extent of their pulsation and structuring into at least three subcategories. This study surveyed 10 years of all-sky camera data to determine the occurrence probability for each type of pulsating aurora in magnetic local time and magnetic latitude. Amorphous pulsating aurora (APAs) are a pervasive, nearly daily feature in the early-morning auroral oval which have an 86 % chance of occurrence at their peak. Patchy pulsating auroras (PPAs) and patchy auroras (PAs) are less common, peaking at 21 % and 29 %, respectively. Before local midnight, pulsating auroras are almost exclusively APAs. Occurrence distributions of APAs, PPAs, and PAs are mapped into the equatorial plane to approximately locate their source regions. The PA and PPA distributions primarily map to locations approximately between 4 and 9 RE, while some APAs map to farther distances, suggesting that the mechanism which structures PPAs and PAs is constrained to the inner magnetosphere. This is in agreement with Grono and Donovan (2019), which located these auroras relative to the proton aurora.

Mid-altitude cusp dynamics and properties during the IMF By dominated intervals

2020 ◽  
Author(s):  
Yulia Bogdanova ◽  
C.-Philippe Escoubet ◽  
Robert Fear ◽  
Karlheinz Trattner ◽  
Jean Berchem ◽  
...  
Keyword(s):  
Local Time ◽  
Large Scale ◽  
Magnetic Local Time ◽  
Plasma Parameters ◽  
Flux Transfer Events ◽  
Cusp Region ◽  
Large Scale Geometry ◽  
Average Size ◽  
String Of Pearls ◽  
The Imf

<p>Observations inside the cusp can be used as distant monitoring of the large-scale geometry and properties of the magnetic reconnection at the magnetopause. The recent modelling and observations of the cusp and flux transfer events in the vicinity of the magnetopause show that the reconnection can occur along the X-line extended over many hours of magnetic local time (MLT), comprising sites of both component and anti-parallel reconnection scenarios. Such observations are in contradiction to the statistical DMSP studies showing that the cusp is rather limited in magnetic local time with an average size 2.5 hours of MLT. Moreover, some past observations indicate that the cusp is moving in response to the changes of the IMF By component, suggesting that the cusp is formed due to anti-parallel reconnection along the X-line limited in MLT.</p><p>In this presentation we analyse several events of the mid-altitude cusp observations during the Cluster campaign when the satellites cross the cusp mainly along the longitude in a string-of-pearls configuration during an Interplanetary Magnetic Field (IMF) configuration with a stable and dominant IMF By-component. During this particular Cluster orbit it was possible to define the dawn and dusk cusp boundaries and to study plasma parameters inside different parts of the cusp region. The observations will be discussed in terms of the cusp extension, cusp motion, and possible formation of the ‘double’ cusp structures. Finally, we will consider what these observations reveal about the large-scale reconnection geometry at the magnetopause.</p>

scholarly journals Climatology of GPS ionospheric scintillations over high and mid-latitude European regions

2009 ◽  
Vol 27 (9) ◽  
pp. 3429-3437 ◽  
Author(s):  
L. Spogli ◽  
L. Alfonsi ◽  
G. De Franceschi ◽  
V. Romano ◽  
M. H. O. Aquino ◽  
...  
Keyword(s):  
Local Time ◽  
Auroral Oval ◽  
Magnetic Local Time ◽  
Ionospheric Scintillation ◽  
Wide Range ◽  
External Conditions ◽  
Ionospheric Scintillations ◽  
Latitudinal Range ◽  
Expected Position ◽  
Analyze Data

Abstract. We analyze data of ionospheric scintillation in the geographic latitudinal range 44°–88° N during the period of October, November and December 2003 as a first step to develop a "scintillation climatology" over Northern Europe. The behavior of the scintillation occurrence as a function of the magnetic local time and of the corrected magnetic latitude is investigated to characterize the external conditions leading to scintillation scenarios. The results shown herein, obtained merging observations from four GISTM (GPS Ionospheric Scintillation and TEC Monitor), highlight also the possibility to investigate the dynamics of irregularities causing scintillation by combining the information coming from a wide range of latitudes. Our findings associate the occurrences of the ionospheric irregularities with the expected position of the auroral oval and ionospheric troughs and show similarities with the distribution in magnetic local time of the polar cap patches. The results show also the effect of ionospheric disturbances on the phase and the amplitude of the GPS signals, evidencing the different contributions of the auroral and the cusp/cap ionosphere.

scholarly journals Surveying pulsating auroras

2019 ◽  
Author(s):  
Eric Grono ◽  
Eric Donovan
Keyword(s):  
Local Time ◽  
Early Morning ◽  
Auroral Oval ◽  
Magnetic Local Time ◽  
Occurrence Probability ◽  
Magnetic Latitude ◽  
Source Regions ◽  
As If

Abstract. The early morning auroral oval is dominated by pulsating auroras. This category of aurora has often been discussed as if it is just one phenomenon, but it is not. Pulsating auroras are separable based on the extent of their pulsation and structuring into at least three subcategories. This study surveyed 10 years of all-sky camera data to determine the occurrence probability for each type of pulsating aurora in magnetic local time and magnetic latitude. Amorphous pulsating aurora is found to be a nearly ubiquitous early morning aurora, and pulsating aurora is almost exclusively amorphous pre-midnight. Occurrence distributions for each type of pulsating aurora are mapped into the magnetosphere to approximately determine the location of their source regions. The patchy and patchy pulsating aurora distributions primarily map to locations approximately between 4 and 9 RE, while some amorphous pulsating aurora maps to farther distances.

scholarly journals The ion experiment onboard the Interball-Aurora satellite; initial results on velocity-dispersed structures in the cleft and inside the auroral oval

1998 ◽  
Vol 16 (9) ◽  
pp. 1056-1069 ◽  
Author(s):  
J. A. Sauvaud ◽  
H. Barthe ◽  
C. Aoustin ◽  
J. J. Thocaven ◽  
J. Rouzaud ◽  
...  
Keyword(s):  
Time Of Flight ◽  
Auroral Oval ◽  
Auroral Zone ◽  
Particle Energy ◽  
Ion Source ◽  
Energy Bands ◽  
Orbit Plane ◽  
Mass Spectrometers ◽  
Auroral Phenomena ◽  
Proton Aurora

Abstract. The Toulouse ION experiment flown on the Russian Interball-Aurora mission performs simultaneous ion and electron measurements. Two mass spectrometers looking in opposing directions perpendicular to the satellite spin axis, which points toward the sun, measure ions in the mass and energy ranges 1–32 amu and ~0–14 000 eV. Two electron spectrometers also looking in opposing directions perform measurements in the energy range ~10 eV–20 000 eV. The Interball-Aurora spacecraft was launched on 29 August 1996 into a 62.8° inclination orbit with an apogee of ~3 RE. The satellite orbital period is 6 h, so that every four orbits the satellite sweeps about the same region of the auroral zone; the orbit plane drifts around the pole in ~9 months. We present a description of the ION experiment and discuss initial measurements performed in the cusp near noon, in the polar cleft at dusk, and inside the proton aurora at dawn. Ion-dispersed energy structures resulting from time-of-flight effects are observed both in the polar cleft at ~16 hours MLT and in the dawnside proton aurora close to 06 hours MLT. Magnetosheath plasma injections in the polar cleft, which appear as overlapping energy bands in particle energy-time spectrograms, are traced backwards in time using a particle trajectory model using 3D electric and magnetic field models. We found that the cleft ion source is located at distances of the order of 18 RE from the earth at about 19 MLT, i.e., on the flank of the magnetopause. These observations are in agreement with flux transfer events (FTE) occurring not only on the front part of the magnetopause but also in a region extending at least to dusk. We also show that, during quiet magnetic conditions, time-of-flight ion dispersions can also be measured inside the dawn proton aurora. A method similar to that used for the cleft is applied to these auroral energy dispersion signatures. Unexpectedly, the ion source is found to be at distances of the order of 60–80 RE, at the dawn flank of the magnetosphere. These results are discussed in terms of possible entry, acceleration, and precipitation mechanisms.Key words. Magnetospheric physics · Auroral phenomena · Energetic particles · Magnetopause · cusp · and boundary layers · Interball-Aurora satellite.

Statistics of pulsating auroras on the basis of all-sky TV data from five stations. I. Occurrence frequency

1981 ◽  
Vol 59 (8) ◽  
pp. 1150-1157 ◽  
Author(s):  
T. Oguti ◽  
S. Kokubun ◽  
K. Hayashi ◽  
K. Tsuruda ◽  
S. Machida ◽  
...  
Keyword(s):  
Local Time ◽  
Cold Plasma ◽  
Geomagnetic Latitude ◽  
Auroral Oval ◽  
Magnetic Activity ◽  
Occurrence Frequency ◽  
Frequency Of Occurrence ◽  
Occurrence Probability ◽  
Energetic Electrons ◽  
Plasma Irregularities

The frequency of occurrence of pulsating auroras is statistically examined on the basis of all-sky TV data for 34 nights from five stations, in a range from 61.5 to 74.3° in geomagnetic latitude. The results are that: (1) occurrence probability of a pulsating aurora is 100% after 4 h in geomagnetic local time, (2) pulsating auroras occur in the morning hours along the auroral oval even when magnetic activity is as small as 0o ≤ Kp ≤ 1, (3) pulsating auroras occur even in the evening when Kp increases to greater than 3−, (4) drift of pulsating auroras is westward in the evening while it is eastward in the morning hours, (5) the region of pulsating auroras splits into two zones, 64 to 68° and 61 to 63° in geomagnetic latitude, after 4 h geomagnetic local time for Kp from 2o to 3−, and the splitting also appears to exist for greater Kp as evidenced by observation other than our auroral data. These results are discussed in relation to distributions of cold plasma irregularities and energetic electrons in the magnetosphere.

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