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.

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.

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.

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 SuperDARN Hokkaido radar observation of westward flow enhancement in subauroral latitudes

2009 ◽  
Vol 27 (4) ◽  
pp. 1695-1699 ◽  
Author(s):  
R. Kataoka ◽  
K. Hosokawa ◽  
N. Nishitani ◽  
Y. Miyoshi
Keyword(s):  
Local Time ◽  
Essential Role ◽  
Ring Current ◽  
Recovery Phase ◽  
Flow Speed ◽  
Magnetic Local Time ◽  
Magnetic Latitude ◽  
Flow Enhancement ◽  
Field Aligned Current ◽  
Hokkaido Radar

Abstract. Westward flow enhancement in subauroral latitudes is investigated based on the first one and a half year observation of the SuperDARN Hokkaido radar. A total of 15 events are identified with the criteria of westward flow speed of >1.0 km/s in magnetic latitude from 45 to 65 deg during geomagnetically disturbed period of Kp>3+ at 20 magnetic local time. It is found that especially during the storm recovery phase, the flow enhancement occurs in broad range of Dst amplitude, and the occurrence latitude depends on the amplitude of Dst. It is also found that the disturbed Kp condition is not sufficient for the appearance of the subauroral flow enhancement as seen by Hokkaido radar while storm-like Dst condition is necessary, supporting the idea that ring current particles play an essential role to enhance the westward flow in subauroral latitudes via magnetosphere-ionosphere coupling through the field-aligned current.

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.

scholarly journals The influence of Titan on Saturn kilometric radiation

2010 ◽  
Vol 28 (2) ◽  
pp. 395-406 ◽  
Author(s):  
J. D. Menietti ◽  
S.-Y. Ye ◽  
C. W. Piker ◽  
B. Cecconi
Keyword(s):  
Radio Emission ◽  
Plasma Wave ◽  
Local Time ◽  
Direction Finding ◽  
Original Study ◽  
Electron Precipitation ◽  
Occurrence Probability ◽  
Source Regions ◽  
Morning Sector ◽  
Field Lines

Abstract. Previous studies have shown that the occurrence probability of Saturn Kilometric Radiation (SKR) appears to be influenced by the local time of Titan. Using a more extensive set of data than the original study, we confirm the correlation of higher occurrence probability of SKR when Titan is located near local midnight. In addition, the direction finding capability of the Cassini Radio Plasma Wave instrument (RPWS) is used to determine if this radio emission emanates from particular source regions. We find that most source regions of SKR are located in the mid-morning sector of local time even when Titan is located near midnight. However, some emission does appear to have a source in the Saturnian nightside, consistent with electron precipitation from field lines that have recently mapped to near Titan.

scholarly journals Cluster observation of few-hour-scale evolution of structured plasma in the inner magnetosphere

2013 ◽  
Vol 31 (9) ◽  
pp. 1569-1578 ◽  
Author(s):  
M. Yamauchi ◽  
I. Dandouras ◽  
H. Rème ◽  
R. Lundin ◽  
L. M. Kistler
Keyword(s):  
Local Time ◽  
Trapped Ions ◽  
Low Energy ◽  
Local Times ◽  
Significant Enhancement ◽  
Occurrence Rate ◽  
Wide Energy Range ◽  
Inner Magnetosphere ◽  
Wide Energy ◽  
Cluster Ion

Abstract. Using Cluster Ion Spectrometry (CIS) data from the spacecraft-4 perigee traversals during the 2001–2006 period (nearly 500 traversals after removing those that are highly contaminated by radiation belt particles), we statistically examined the local time distribution of structured trapped ions at sub- to few-keV range as well as inbound–outbound differences of these ion signatures in intensities and energy–latitude dispersion directions. Since the Cluster orbit during this period was almost constant and approximately north–south symmetric at nearly constant local time near the perigee, inbound–outbound differences are attributed to temporal developments in a 1–2 h timescale. Three types of structured ions at sub- to few keV range that are commonly found in the inner magnetosphere are examined: – Energy–latitude dispersed structured ions at less than a few keV, – Short-lived dispersionless ion stripes at wide energy range extending 0.1–10 keV, – Short-lived low-energy ion bursts at less than a few hundred eV. The statistics revealed that the wedge-like dispersed ions are most often observed in the dawn sector (60% of traversals), and a large portion of them show significant enhancement during the traversals at all local times. The short-lived ion stripes are predominantly found near midnight, where most stripes are significantly enhanced during the traversals and are associated with substorm activities with geomagnetic AL < −300 nT. The low-energy bursts are observed at all local times and under all geomagnetic conditions, with moderate peak of the occurrence rate in the afternoon sector. A large portion of them again show significant enhancement or decay during the traversals.

Sign in / Sign up

Export Citation Format

Share Document