The Variation of Ionospheric O+ and H+ Outflow during Sawtooth Oscillations

2021 ◽  
Author(s):  
Niloufar Nowrouzi ◽  
Lynn Kistler ◽  
Eric Lund ◽  
Kai Zhao
Keyword(s):  
Plasma Sheet ◽  
Statistical Study ◽  
Onset Time ◽  
Direct Access ◽  
Data Set ◽  
Superposed Epoch Analysis ◽  
3D Data ◽  
Before And After ◽  
Epoch Analysis ◽  
Sawtooth Oscillations

<p>Sawtooth events are repeated injections of energetic particles at geosynchronous orbit. Although studies have shown that 94% of sawtooth events occur during  magnetic storm times, the main factor that causes a sawtooth event is unknown. Simulations have suggested that heavy ions like O<sup>+</sup> may play a role in driving the sawtooth mode by increasing the magnetotail pressure and causing the magnetic tail to stretch. O<sup>+</sup> ions located in the nightside auroral region have a direct access to the near-earth plasma-sheet. O<sup>+</sup> in the dayside cusp can reach to the midtail plasma-sheet when the convection velocity is sufficiently strong. Whether the dayside or nightside source is more important is not known.</p><p>We show results of a statistical study of the variation of the O+ and H+ outflow flux during sawtooth events for SIR and ICME sawtooth events. We perform a superposed epoch analysis of the ion outflow using the TEAMS (Time-of-Flight Energy Angle Mass Spectrograph) instrument on the FAST spacecraft. TEAMS measures the ion composition over the energy range of 1 eV e<sup>-1</sup> to 12 keV e<sup>-1</sup>.  We have done major corrections and calibrations (producing 3D data set, anode calibration, mass classification, removing ram effect and incorporating dead time corrections) on TEAMS data and produced a data set for four data species (H<sup>+</sup>, O<sup>+</sup>, and He<sup>+</sup>). From 1996 to 2007, we have data for 133 orbits of CME-driven and for 103 orbits of SIR-driven sawtooth events with an altitude above 1500 km. We found that:</p><ul><li>the averaged O<sup>+</sup> outflow flux is more intense in the cusp dayside than in the nightside, before and after onset time.</li> <li><span>Before onset, an intense averaged outflow flux in the dawnside of CME events is seen. This outflow decreases after onset time.</span></li> <li><span>In both CME-driven and SIR-driven, the averaged O</span><sup>+</sup><span> outflow increases after onset time, in the nightside, cusp dayside. This increase is greater on the nightside than in the cusp.</span></li> </ul><p>We will develop this study by performing a similar statistical study for H<sup>+</sup> outflow and finally will compare the H<sup>+</sup> result with the O<sup>+ </sup>result.</p>

scholarly journals Response of middle atmospheric temperature to the solar 27-day cycle: an analysis of 13 years of MLS data

2019 ◽  
Author(s):  
Piao Rong ◽  
Christian von Savigny ◽  
Chunmin Zhang ◽  
Christoph G. Hoffmann ◽  
Michael J. Schwartz
Keyword(s):  
Atmospheric Temperature ◽  
Significance Test ◽  
Test Method ◽  
Data Set ◽  
Superposed Epoch Analysis ◽  
Model Studies ◽  
Window Width ◽  
Higher Temperature ◽  
Time Lagged ◽  
Epoch Analysis

Abstract. This work focuses on studying the presence and characteristics of solar 27-day signatures in middle atmospheric temperature observed by the Microwave Limb Sounder (MLS) on NASA’s Aura spacecraft. The 27-day signatures in temperature are extracted using the superposed epoch analysis (SEA) technique. We use time-lagged linear regression (sensitivity analysis) and a Monte-Carlo test method (significance test) to explore the dependence of the results on latitude and altitude, on solar activity and season, as well as on different parameters (e.g., smoothing filter, window width and epoch centers). Using different parameters does impact the results to a certain degree, but it does not affect the overall results. Analyzing the 13-year data set shows that highly significant solar 27-day signatures in middle atmospheric temperature are present at many altitudes and latitudes. A tendency to higher temperature sensitivity to solar forcing in the winter hemisphere is found. In addition, the sensitivity of temperature to solar 27-day forcing tends to be larger at high latitudes than at low latitudes. For solar 11-year minimum conditions no statistically significant identification of a solar 27-day signature is possible at most altitudes and latitudes. Several results we obtained suggest that processes other than solar variability drive atmospheric temperature variability at periods around 27-days. Comparisons of the obtained sensitivity values with earlier experimental and model studies show good overall agreement.

scholarly journals A superposed epoch analysis of auroral evolution during substorm growth, onset and recovery: open magnetic flux control of substorm intensity

2009 ◽  
Vol 27 (2) ◽  
pp. 659-668 ◽  
Author(s):  
S. E. Milan ◽  
A. Grocott ◽  
C. Forsyth ◽  
S. M. Imber ◽  
P. D. Boakes ◽  
...  
Keyword(s):  
Magnetic Flux ◽  
Ring Current ◽  
Low Latitude ◽  
Superposed Epoch Analysis ◽  
Before And After ◽  
Open Magnetic Flux ◽  
Open Flux ◽  
Epoch Analysis ◽  
Proton Aurora ◽  
Current Systems

Abstract. We perform two superposed epoch analyses of the auroral evolution during substorms using the FUV instrument on the Imager for Magnetopause-to-Aurora Global Explorer (IMAGE) spacecraft. The larger of the two studies includes nearly 2000 substorms. We subdivide the substorms by onset latitude, a measure of the open magnetic flux in the magnetosphere, and determine average auroral images before and after substorm onset, for both electron and proton aurora. Our results indicate that substorms are more intense in terms of auroral brightness when the open flux content of the magnetosphere is larger, and that magnetic flux closure is more significant. The increase in auroral brightness at onset is larger for electrons than protons. We also show that there is a dawn-dusk offset in the location of the electron and proton aurora that mirrors the relative locations of the region 1 and region 2 current systems. Superposed epoch analyses of the solar wind, interplanetary magnetic field, and geomagnetic indices for the substorms under study indicate that dayside reconnection is expected to occur at a faster rate prior to low latitude onsets, but also that the ring current is enhanced for these events.

Evaluation of Aurora Activity Obtained from Abisko and Kiruna Ground Based Observation

2020 ◽  
Author(s):  
Kiyonobu Sugihara ◽  
Masatoshi Yamauchi ◽  
Makoto Kobayashi ◽  
Shin Koichi ◽  
Masahiro Nishi
Keyword(s):  
Three Dimensional ◽  
Dimensional Structure ◽  
Color Code ◽  
Camera System ◽  
Superposed Epoch Analysis ◽  
Simple Index ◽  
Linear Distance ◽  
Magnetic Variation ◽  
Before And After ◽  
Epoch Analysis

<p>Available space weather forecasts mainly use data from the Sun and upstream interplanetary monitoring, to provide the early warning. Although the accuracy is improving, it cannot provide onset timing and actual strength of the substorm and its propagations better than 1 hour. A higher-accuracy forecast requires monitoring of the ionosphere (e.g., aurora and geomagnetic field). In this sense, it is also necessary to develop a value-based nowcast based on such monitoring. In EGU 2018, Yamauchi et al. has proposed simple index showing aurora and geomagnetic conditions using 1-minute resolution values from Kiruna. This study improved in the following directions:</p><p>(1) We used 1-sec resolution data and optimized the indices above: By using 1-sec values, the products representing variation (standard deviation and peak-to-peak variation) can be obtained every minute and improved, whereas combination of <em>∑L</em><sup>3</sup> (or ∑<em>L*</em>exp(<em>L</em>)) and area of aurora found to be the best in representing the aurora activity, where <em>L</em> is luminosity of each pixel defined by HLS color code. Using these values, we confirmed that the intensity of the aurora was different for the same magnetic variation between before and after the strongest aurora (substorm onset). Therefore, it is necessary to add a condition of "increasing trend" of both aurora and magnetic variation from the viewpoint of forecasting.</p><p>(2) We compared the results from two different places (Abisko and Kiruna in Sweden) that are 89 km apart in linear distance. Our Abisko camera system (DASC, Digital All Sky Camera) is in operation since March 2014. When the aurora was observed at both sites, the shapes of the aurora at both sites are sometimes quite different at the same time. In addition, the timing of the brightest aurora (<em>∑L</em><sup>3</sup> or <em>∑L*</em>exp(<em>L</em>) is maximum) was different between both sites. These results confirm that the aurora had a three-dimensional structure, which has been known for many years.</p><p>(3) Using superposed epoch analysis, we also took statistics of last 10 minutes before the largest aurora (in the index mentioned above) occurred.</p>

scholarly journals A Statistical Study of the Correlation between Geomagnetic Storms and M ≥ 7.0 Global Earthquakes during 1957–2020

Entropy ◽  
2020 ◽  
Vol 22 (11) ◽  
pp. 1270
Author(s):  
Hongyan Chen ◽  
Rui Wang ◽  
Miao Miao ◽  
Xiaocan Liu ◽  
Yonghui Ma ◽  
...  
Keyword(s):  
Electroosmotic Flow ◽  
Statistical Study ◽  
Geomagnetic Storms ◽  
Statistical Correlation ◽  
Superposed Epoch Analysis ◽  
Significance Analysis ◽  
Complex Process ◽  
Shallow Earthquakes ◽  
Statistical Studies ◽  
Epoch Analysis

In order to find out whether the geomagnetic storms and large-mega earthquakes are correlated or not, statistical studies based on Superposed Epoch Analysis (SEA), significance analysis, and Z test have been applied to the Dst index data and M ≥ 7.0 global earthquakes during 1957–2020. The results indicate that before M ≥ 7.0 global earthquakes, there are clearly higher probabilities of geomagnetic storms than after them. Geomagnetic storms are more likely to be related with shallow earthquakes rather than deep ones. Further statistical investigations of the results based on cumulative storm hours show consistency with those based on storm days, suggesting that the high probability of geomagnetic storms prior to large-mega earthquakes is significant and robust. Some possible mechanisms such as a reverse piezoelectric effect and/or electroosmotic flow are discussed to explain the statistical correlation. The result might open new perspectives in the complex process of earthquakes and the Lithosphere-Atmosphere-Ionosphere (LAI) coupling.

scholarly journals Superposed epoch analysis of dense plasma access to geosynchronous orbit

2005 ◽  
Vol 23 (7) ◽  
pp. 2519-2529 ◽  
Author(s):  
B. Lavraud ◽  
M. H. Denton ◽  
M. F. Thomsen ◽  
J. E. Borovsky ◽  
R. H. W. Friedel
Keyword(s):  
Plasma Sheet ◽  
Ring Current ◽  
Dense Plasma ◽  
Transport Processes ◽  
Geosynchronous Orbit ◽  
Plasma Convection ◽  
Tail Region ◽  
Superposed Epoch Analysis ◽  
Magnetospheric Convection ◽  
Epoch Analysis

Abstract. We report on the occurrence of dense plasma access to geosynchronous orbit. We performed a superposed epoch analysis of 1464 events of dense (>2 cm–3 at onset) plasma observed by the MPA instruments on board the Los Alamos satellites, for the period 1990–2002. The results allow us to study the temporal evolution of various plasma parameters as a function of local time. We show that dense plasma access to geosynchronous orbit mostly occurs near local midnight. This dense plasma population is shown to be freshly injected from the mid-tail region, colder than the typical plasma sheet and composed of a relatively small O+ component. This population is thus probably the result of a cold, dense plasma sheet (CDPS) injection from the mid-tail region. Cold and dense ion populations are also observed on the dawnside of geosynchronous orbit at a similar epoch time. However, we demonstrate that this latter population is not the result of the dawnward transport of the population detected near midnight. The properties of this ion population may arise from the contribution of both ionospheric upflows and precipitating plasma sheet material. The correlation of an enhanced Kp index with the arrival of the CDPS at geosynchronous orbit shows that the inward transport of this population is allowed by an enhanced magnetospheric convection. Surprisingly, this dense plasma does not, in general, lead to a stronger Dst (ring current strength) within the 12 h following the CDPS injection. It is noted, however, that the superposed Kp index returns to relatively low values soon after the arrival of the CDPS. This may suggest that the dense plasma is, given the average of the 1464 events of this study, only transiting through geosynchronous orbit without accessing the inner regions and, therefore, does not contribute to the ring current. Keywords. Magnetospheric physics (Plasma convection; Plasma sheet) – Space plasma physics (Transport processes)

Superposed epoch analysis of the substorm plasma sheet

1991 ◽  
Vol 96 (A7) ◽  
pp. 11605 ◽  
Author(s):  
W. Baumjohann ◽  
G. Paschmann ◽  
T. Nagai ◽  
H. Lühr
Keyword(s):  
Plasma Sheet ◽  
Superposed Epoch Analysis ◽  
Epoch Analysis

scholarly journals Statistical visualization of the Earth's magnetotail and the implied mechanism of substorm triggering based on superposed-epoch analysis of THEMIS data

2014 ◽  
Vol 32 (2) ◽  
pp. 99-111 ◽  
Author(s):  
S. Machida ◽  
Y. Miyashita ◽  
A. Ieda ◽  
M. Nosé ◽  
V. Angelopoulos ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Plasma Sheet ◽  
Time Lag ◽  
Elevation Angle ◽  
Substorm Onset ◽  
Boundary Layer Flows ◽  
Superposed Epoch Analysis ◽  
Current Disruption ◽  
Central Plasma ◽  
Epoch Analysis

Abstract. To investigate the physical mechanism responsible for substorm triggering, we performed a superposed-epoch analysis using plasma and magnetic-field data from THEMIS probes. Substorm onset timing was determined based on auroral breakups detected by all-sky imagers at the THEMIS ground-based observatories. We found earthward flows associated with north–south auroral streamers during the substorm growth phase. At around X = −12 Earth radii (RE), the northward magnetic field and its elevation angle decreased markedly approximately 4 min before substorm onset. Moreover, a northward magnetic-field increase associated with pre-onset earthward flows was found at around X = −17 RE. This variation indicates that local dipolarization occurs. Interestingly, in the region earthwards of X = −18 RE, earthward flows in the central plasma sheet (CPS) reduced significantly approximately 3 min before substorm onset, which was followed by a weakening of dawn-/duskward plasma-sheet boundary-layer flows (subject to a 1 min time lag). Subsequently, approximately 1 min before substorm onset, earthward flows in the CPS were enhanced again and at the onset, tailward flows started at around X = −20 RE. Following substorm onset, an increase in the northward magnetic field caused by dipolarization was found in the near-Earth region. Synthesizing these results, we confirm our previous results based on GEOTAIL data, which implied that significant variations start earlier than both current disruption and magnetic reconnection, at approximately 4 min before substorm onset roughly halfway between the two regions of interest; i.e. in the catapult current sheet.

scholarly journals Statistical analysis of magnetotail fast flows and related magnetic disturbances

2016 ◽  
Vol 34 (4) ◽  
pp. 399-409 ◽  
Author(s):  
Dennis Frühauff ◽  
Karl-Heinz Glassmeier
Keyword(s):  
Flow Direction ◽  
Background Field ◽  
Minimum Variance ◽  
Data Set ◽  
Superposed Epoch Analysis ◽  
Maximum Variance ◽  
Hydrodynamical Simulations ◽  
Epoch Analysis ◽  
Fast Flow ◽  
Group Structures

Abstract. This study presents an investigation on the occurrence of fast flows in the magnetotail using the complete available data set of the THEMIS spacecraft for the years 2007 to 2015. The fast flow events (times of enhanced ion velocity) are detected through the use of a velocity criterion, therefore making the resulting database as large as almost 16 000 events. First, basic statistical findings concerning velocity distributions, occurrence rates, group structures are presented. Second, Superposed Epoch Analysis is utilized to account for average profiles of selected plasma quantities. The data reveal representative time series in near and far tail of the Earth with typical timescales of the order of 1–2 min, corresponding to scale sizes of 3 RE. Last, related magnetic field disturbances are analyzed. It is found that the minimum variance direction is essentially confined to a plane almost perpendicular to the main flow direction while, at the same time, the maximum variance direction is aligned with flow and background field directions. The presentation of the database and first statistical findings will prove useful both as input for magneto-hydrodynamical simulations and theoretical considerations of fast flows.

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