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.

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.

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.

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 The effects of an interplanetary shock on the high-latitude ionospheric convection during an IMF <I>B<sub>y</sub></I>-dominated period

2008 ◽  
Vol 26 (9) ◽  
pp. 2937-2951 ◽  
Author(s):  
I. Coco ◽  
E. Amata ◽  
M. F. Marcucci ◽  
D. Ambrosino ◽  
J.-P. Villain ◽  
...  
Keyword(s):  
High Latitude ◽  
Geomagnetic Field ◽  
Dynamic Pressure ◽  
Interplanetary Shock ◽  
Ionospheric Convection ◽  
Vortical Structures ◽  
Magnetometer Data ◽  
Northern High Latitude ◽  
Lobe Reconnection ◽  
Very High

Abstract. On 6 January 1998 an interplanetary shock hit the magnetosphere around 14:15 UT and caused a reconfiguration of the northern high-latitude ionospheric convection. We use SuperDARN, spacecraft and ground magnetometer data to study such reconfiguration. We find that the shock front was tilted towards the morning flank of the magnetosphere, while the Interplanetary Magnetic Field (IMF) was By-dominated, with By<0, IMF Bz>0 and |By|>>Bz. As expected, the magnetospheric compression started at the first impact point of the shock on the magnetopause causing an increase of the Chapman-Ferraro current from dawn to dusk and yielding an increase of the geomagnetic field at the geostationary orbit and on the ground. Moreover, the high-latitude magnetometer data show vortical structures clearly related to the interaction of the shock with the magnetosphere-ionosphere system. In this context, the SuperDARN convection maps show that at very high latitudes above the northern Cusp and in the morning sector, intense sunward convection fluxes appear, well correlated in time with the SI arrival, having a signature typical for Bz>0 dominated lobe reconnection. We suggest that in this case the dynamic pressure increase associated to the shock plays a role in favouring the setting up of a new lobe merging line albeit |By|>>Bz≥0.

scholarly journals The association between giant pulsations (Pgs) and the auroral oval

1994 ◽  
Vol 12 (7) ◽  
pp. 649-654 ◽  
Author(s):  
G. Chisham ◽  
D. Orr
Keyword(s):  
Plasma Sheet ◽  
Geomagnetic Latitude ◽  
Early Morning ◽  
Auroral Oval ◽  
Resonant Field ◽  
Morning Sector ◽  
Field Lines ◽  
Giant Pulsations ◽  
Latitudinal Band

Abstract. Two features of giant pulsations (Pgs) which still require an explanation are firstly, why Pgs occur mainly in the early morning sector (i.e. 03:00-07:00 MLT) and not at other times of day, and secondly, why Pgs occur preferentially in a narrow latitudinal band (approximately 63°-68° geomagnetic latitude). Using statistics from 34 Pg events observed by the EISCAT magnetometer cross, a comparison has been made between the location of the Pg resonant field lines and the equatorward edge of the auroral oval. The majority of these Pg events appear to occur just poleward of this boundary. Using these results, an explanation of the two features of Pgs as detailed above is made. This explanation involves the interaction of protons, which may be responsible for the Pg events, with the inner edge of the plasma sheet or with its ionospheric equivalent, the equatorward edge of the auroral oval.

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 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 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.

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