Recurrent substorm activity during the passage of a corotating interaction region

We present a statistical study of relativistic electron counts in the electron radiation belt across a range of drift shells (L * > 4) combining data from nine combined X-ray dosimeters (CXD) on the global positioning system (GPS) constellation. The response of the electron counts as functions of time, energy and drift shell are examined statistically for 67 solar wind stream interfaces (SIs); two-dimensional superposed epoch analysis is performed with the CXD data. For these epochs we study the radiation belt dropouts and concurrent variations in key geophysical parameters.At higher L * we observe a tendency for a gradual drop in the electron counts over the day preceding the SI, consistent with outward diffusion and magnetopause shadowing. At all L * , dropouts occur with a median time scale of 7 h and median counts fall by 0.4-1.8 orders of magnitude. The central tendencies of radiation belt dropout and recovery depend on both L * and energy. For 70 per cent of epochs Sym-H more than −30 nT, yet only three of 67 SIs did not have an associated dropout in the electron data. Statistical maps of electron precipitation suggest that chorus-driven relativistic electron microbursts might be major contributors to radiation belt losses under high-speed stream driving.

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“…Recurrent substorms are known to be common under high-speed stream driving (e.g. Morley et al 2009b).…”

Section: Stream Interfacesmentioning

confidence: 99%

Dropouts of the outer electron radiation belt in response to solar wind stream interfaces: global positioning system observations

et al. 2010

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“…The AE indices (not shown) were also inspected for geomagnetic activity. The AU and AL indices indicate periodic enhanced auroral activity through the main phase and early recovery phase of the storm, most probably substorm related [e.g., Morley, 2008]. The SYM-H index remained depressed over the period of study indicating that the ring current was slightly enhanced.…”

Section: Interplanetary Magnetic Field and Indicesmentioning

confidence: 99%

Multipoint observations of Pc1‐2 waves in the afternoon sector

et al. 2009

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[1] Coordinated observations from GOES-9, DMSP F-13, and Chokurdakh (CHD) have shown concurrent Pc1-2 band wave activity in the late afternoon sector, close to 16 MLT. The left-hand polarization of the waves in space indicates that these are electromagnetic ion cyclotron (EMIC) waves. In the region of field line conjunction, DMSP also observed 6-30 keV energy ion precipitation. We have examined the propagation of the EMIC waves from the magnetosphere to the ionosphere using both time series analysis and a 2 1 2 -D magnetohydrodynamic model. Our analysis suggests that the EMIC are generated by interactions with cold plasma within a drainage plume, consistent with theory, and that the waves primarily propagate earthward along geomagnetic field lines at the eastward (outer) edge of the plume.

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“…Substorms in corotating interaction region‐ and coronal mass ejection‐driven storms tend to recur quasi‐periodically on a time scale of 2–4 hr (Huang et al, ; Lee et al, ). In these cases, Morley et al () suggest some predictability of individual onsets if not amplitudes. More generally, only the statistics of substorm recurrence and amplitude have been successfully reproduced, rather than individual substorm onset times and sizes (Freeman & Morley, ; Morley et al, ).…”

Section: Introductionmentioning

confidence: 99%

The Influence of Substorms on Extreme Rates of Change of the Surface Horizontal Magnetic Field in the United Kingdom

2019

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We investigate how statistical properties of the rate of change R of the surface horizontal magnetic field in the United Kingdom differ during substorm expansion and recovery phases compared with other times. R is calculated from 1‐min magnetic field data from three INTERMAGNET observatories—Lerwick, Eskdalemuir, and Hartland and between 1996 and 2014—nearly two solar cycles. Substorm expansion and recovery phases are identified from the SuperMAG Lower index using the Substorm Onsets and Phases from Indices of the Electrojet method. The probability distribution of R is decomposed into categories of whether during substorm expansion and recovery phases, in enhanced convection intervals, or at other times. From this, we find that 54–56% of all extreme R values (defined as above the 99.97th percentile) occur during substorm expansion or recovery phases. By similarly decomposing the magnetic local time variation of the occurrence of large R values (>99th percentile), we deduce that 21–25% of large R during substorm expansion and recovery phases are attributable to the Disturbance Polar (DP)1 magnetic perturbation caused by the substorm current wedge. This corresponds to 10–14% of all large R in the entire data set. These results, together with asymptotic trends in occurrence probabilities, may indicate the two‐cell DP2 magnetic perturbation caused by magnetospheric convection as the dominant source of hazardous R > 600 nT/min that is potentially damaging to the U.K. National Grid. Thus, further research is needed to understand and model DP2, its mesoscale turbulent structure, and substorm feedbacks in order that GIC impact on the National Grid may be better understood and predicted.

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Recurrent substorm activity during the passage of a corotating interaction region

Cited by 22 publications

References 42 publications

Dropouts of the outer electron radiation belt in response to solar wind stream interfaces: global positioning system observations

Dropouts of the outer electron radiation belt in response to solar wind stream interfaces: global positioning system observations

Multipoint observations of Pc1‐2 waves in the afternoon sector

The Influence of Substorms on Extreme Rates of Change of the Surface Horizontal Magnetic Field in the United Kingdom

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