Detailed Regression Model of Plasma Sheet B_y

Abstract

In a statistical model plasma sheet By primarily depends on interplanetary magnetic field (IMF) Byi and geodipole tilt τ. With 11 years of Geotail measurements we investigate a role of several other parameters with a linear regression model. Optimal averaging window of IMF input, maximizing correlation and regression coefficients, is found to be 2.25 hr. Influence of IMF Bzi and local Bz on IMF penetration (regression with regard to Byi) and the deviations from the predefined warp deformation are at the level 5–10% relative to the primary model coefficients. The IMF penetration beyond 25 RE is somewhat larger for northward IMF, while closer to the Earth it becomes somewhat larger for southward IMF. These smaller effects turned out to be rather uneven across the tail, making reliable quantification and physical interpretation not always possible. The major reasons of difficulties are uneven coverage and internal correlations in the input space ( Byi–τ– Bzi) due to combination of spacecraft orbit and neutral sheet dynamics, effects of coordinate transformations, etc. In particular, origins of extremely large IMF Byi penetration (order of 30–50% above the average one) for some years and tail locations remain not fully clear. A larger multispacecraft data set covering all seasons in all spatial zones is necessary to further advance in this study.

Magnetospheric “Penetration” of IMF Viewed Through the Lens of an Empirical RBF Modeling

“…Note in this regard that a qualitatively similar result was found by Tenfjord et al (2017Tenfjord et al ( , 2018 and Cao et al (2014). Petrukovich and Lukin (2018) also reported a stronger penetration during southward IMF B z at r ≤ 25 R E .…”

“…First, the induced B is not limited to only the nightside but extends throughout the entire equatorial magnetosphere. Petrukovich and Lukin (2018) also reported a stronger penetration during southward IMF B z at r ≤ 25 R E . As far as we know, the IMF B effects in the near-equatorial dayside region were studied only on the basis of geostationary measurements (Tenfjord et al, 2017(Tenfjord et al, , 2018Wing et al, 1995) and our obtained penetration coefficients 0.2-0.4 agree with those previous results.…”

“…With regard to the spatial distribution of the induced , the most comprehensive statistics for the midtail region ( 31 10 ) was presented by Petrukovich (, ) and Petrukovich and Lukin () on the basis of Geotail data. At closer distances, the studies have either been limited to MHD simulations (Tenfjord et al, , ) or made on the basis of only synchronous data (Cowley & Hughes, ; Tenfjord et al, , ; Wing et al, ).…”

Convection in the Magnetosphere‐Ionosphere System: A Multimission Survey of Its Response to IMF By Reversals

“…However, in a later study investigating “slow flows,” Pitkänen et al (2019) use a 15 min average taken 135 min prior to the corresponding data measurement in the tail. They cite the result of Petrukovich and Lukin (2018), who developed a linear regression model of the plasma sheet B y component with respect to the IMF B y component using Geotail data, as justification for this.…”

IMF By Influence on Magnetospheric Convection in Earth's Magnetotail Plasma Sheet

“…In this study, we average the IMF over a 15-min time interval 135 min prior to the tail measurement. This averaging window was obtained as optimal by Petrukovich and Lukin (2018), who studied the correlation between IMF B y and tail B y with different time delays for all IMF B z conditions and in similar tail distances to the present study.…”