Correspondence between the ULF wave power spatial distribution and auroral oval boundaries

Козырева, О. В.; Пилипенко, В. А.; Pilipenko, Vyacheslav; Engebretson, M. J.; Климушкин, Дмитрий; Klimushkin, D. Yu.; Mager, P. N.

doi:10.12737/16848

Cited by 8 publications

(4 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Furthermore, if the dawn-dusk asymmetry were predominantly due to asymmetries in ionospheric conductivity we would see the asymmetry for more parameters and latitudes than in our analysis above. However, the relationship between ionospheric conductivity and solar wind properties (e.g., Newell et al, 2009) and the related effect of the auroral oval on observed wave power (Kozyreva et al, 2016;Pilipenko et al, 2001;Simms et al, 2006) are likely to have additional effects that should be investigated in future, perhaps with a secondary set of hypotheses, or with an expanded set of parameters if they could be causally established.…”

Section: Hypotheses 2: Power Signature Of External Driversmentioning

confidence: 99%

Random Forest Model of Ultralow‐Frequency Magnetospheric Wave Power

Bentley

Stout

Bloch

et al. 2020

Earth and Space Science

View full text Add to dashboard Cite

Models of magnetospheric ultralow-frequency (ULF) waves can be used to study wave phenomena and to calculate the effect of these waves on the energization and transport of radiation belt electrons. We present a decision tree ensemble (i.e., a random forest) model of ground-based ULF wave power spectral density driven by solar wind speed v sw , north-south component of the interplanetary magnetic field Bz, and variance of proton number density var(Np). This model corresponds to four radial locations in the magnetosphere (roughly L ∼ 4.21 to 7.94) and spans 1-15 mHz, with hourly magnetic local time resolution. The decision tree ensembles are easier to use than the previous model generation; they have better coverage, perform better at predicting power, and have reduced error due to intelligently chosen bins in parameter space. We outline the difficulties in extracting physics from parameterized models and demonstrate a hypothesis testing framework to iteratively explore finer driving processes. We confirm a regime change for ULF driving about Bz = 0. We posit that ULF wave power directly driven by magnetopause perturbations corresponds to a latitude-dependent dawn-dusk asymmetry, which we see with increasing speed. Model uncertainty identifies where the underlying physics is not fully captured; we find that power due to substorms is less well characterized by Bz > 0, with an effect that is seen globally and not just near midnight. The largest uncertainty is seen for the smallest amounts of solar wind driving, suggesting that internal magnetospheric properties may play a significant role in ULF wave occurrence. Plain Language Summary To describe the energy and motion of electrons in the radiation belts for space weather modeling purposes, we need to be able to describe the large-scale ultralow-frequency plasma waves. These waves can energize and transport high-energy electrons, which pose a hazard to spacecraft. Using ground-based magnetometers whose observations directly correspond to waves in space, we construct a machine learning model that predicts power in those waves based on incoming solar wind properties. This performs better than the previous model and is more easily used to investigate the physics. We demonstrate how to use it to explore the physics by comparing it to existing wave phenomena. We find that the solar wind drives it in the ways expected but that we should not average over these processes as some of them have a significant on/off switch. We find that two aspects of magnetospheric physics are not fully captured in our model and contribute to the remaining uncertainty: the effect of substorms throughout the magnetosphere and the internal state of the magnetosphere. These are likely to have a significant additional impact on wave occurrence.

show abstract

Section: Hypotheses 2: Power Signature Of External Driversmentioning

confidence: 99%

Random Forest Model of Ultralow‐Frequency Magnetospheric Wave Power

Bentley

Stout

Bloch

et al. 2020

Earth and Space Science

View full text Add to dashboard Cite

show abstract

“…d. Maps of magnetic perturbations and the synoptic open/?closed boundary of the magnetosphere in both polar caps (Urban et al, 2011). e. Statistical maps of magnetic perturbations (Pothier et al, 2015;Weimer et al, 2010) (Kozyreva et al, 2016) and other ULF wave categories superposed on magnetospheric regions such as the polar cap, auroral zone, plasmatrough, and plasmasphere. g. Global and regional maps and parameterizations of geomagnetic disturbances (and time derivatives) that drive ground-induced currents (e.g., Carter et al, 2016;Love et al, 2016;Woodroffe et al, 2016).…”

Section: Higher-level Data Productsmentioning

confidence: 99%

The Future of Ground Magnetometer Arrays in Support of Space Weather Monitoring and Research

Engebretson

Zesta

2017

Space Weather

Self Cite

View full text Add to dashboard Cite

A community workshop was held in Greenbelt, Maryland, on 5–6 May 2016 to discuss recommendations for the future of ground magnetometer array research in space physics. The community reviewed findings contained in the 2016 Geospace Portfolio Review of the Geospace Section of the Division of Atmospheric and Geospace Science of the National Science Foundation and discussed the present state of ground magnetometer arrays and possible pathways for a more optimal, robust, and effective organization and scientific use of these ground arrays. This paper summarizes the report of that workshop to the National Science Foundation (Engebretson & Zesta, ) as well as conclusions from two follow‐up meetings. It describes the current state of U.S.‐funded ground magnetometer arrays and summarizes community recommendations for changes in both organizational and funding structures. It also outlines a variety of new and/or augmented regional and global data products and visualizations that can be facilitated by increased collaboration among arrays. Such products will enhance the value of ground‐based magnetometer data to the community's effort for understanding of Earth's space environment and space weather effects.

show abstract

“…A demarcation of the cusp soft electron precipitation can be determined by comparing the equatorward boundary of the red (630.0 nm) auroral emission along the photometer meridian scanning [Lorentzen et al, 1996]. Precipitation of soft electrons with 0.1-1 keV energies is a good indicator of open magnetic field lines and corresponds to the cusp aurora dominated by the red emission (Rayleigh intensity ratio 630.0/557.7>1) [Lorentzen, Moen, 2000;Johnsen, Lorentzen, 2012]. However, dayside auroral optical measurements can be made during winter months only.…”

Section: Ionospheric Footprint Of the Dayside Ocb From Optical And Hfmentioning

confidence: 99%

“…Geomagnetic pulsations in the Pc5-6 band (periods about 3-15 min) have been known to be a persistent feature of the ULF activity at dayside high latitudes [Engebretson et al, 1995;Francia et al, 2005]. Morphologically, these high-latitude long-period pulsations (sometimes called Irregular Pulsations at Cusp Latitudes [Bolshakova et al, 1988]) differ from well-known quasi-monochromatic Pc5 waves observed at auroral latitudes [Kozyreva et al, 2016]. The specific high-latitude near-noon pulsations could be a signature of the magnetopause surface eigenmodes [Plaschke et al, 2009a;Hartinger et al, 2015] or oscillations of the last field lines [Lanzerotti et al, 1999;Urban et al, 2011].…”

Section: High-latitude Ulf Wave Activity As a Possible Ocb Discriminatormentioning

confidence: 99%

Suppression of the dayside magnetopause surface modes

Пилипенко

Pilipenko

Козырева

et al. 2017

Solnechno-Zemnaya Fizika

Self Cite

View full text Add to dashboard Cite

Magnetopause surface eigenmodes were suggested as a potential source of dayside high-latitude broadband pulsations in the Pc5-6 band (frequency about 1–2 mHz). However, the search for a ground signature of these modes has not provided encouraging results. The comparison of multi-instrument data from Svalbard with the latitudinal structure of Pc5-6 pulsations, recorded by magnetometers covering near-cusp latitudes, has shown that often the latitudinal maximum of pulsation power occurs about 2–3° deeper in the magnetosphere than the dayside open-closed field line boundary (OCB). The OCB proxy was determined from SuperDARN radar data as the equatorward boundary of enhanced width of a return radio signal. The OCB-ULF correspondence is further examined by comparing the latitudinal profile of the near-noon pulsation power with the equatorward edge of the auroral red emission from the meridian scanning photometer. In most analyzed events, the “epicenter” of Pc5-6 power is at 1–2° lower latitude than the optical OCB proxy. Therefore, the dayside Pc5-6 pulsations cannot be associated with the ground image of the magnetopause surface modes or with oscillations of the last field line. A lack of ground response to these modes beneath the ionospheric projection of OCB seems puzzling. As a possible explanation, we suggest that a high variability of the outer magnetosphere near the magnetopause region may suppress the excitation efficiency. To quantify this hypothesis, we consider a driven field line resonator terminated by conjugate ionospheres with stochastic fluctuations of its eigenfrequency. A solution of this problem predicts a substantial deterioration of resonant properties of MHD resonator even under a relatively low level of background fluctuations. This effect may explain why there is no ground response to magnetopause surface modes or oscillations of the last field line at the OCB latitude, but it can be seen at somewhat lower latitudes with more regular and stable magnetic and plasma structure.

show abstract

Correspondence between the ULF wave power spatial distribution and auroral oval boundaries

Cited by 8 publications

References 34 publications

Random Forest Model of Ultralow‐Frequency Magnetospheric Wave Power

Random Forest Model of Ultralow‐Frequency Magnetospheric Wave Power

The Future of Ground Magnetometer Arrays in Support of Space Weather Monitoring and Research

Suppression of the dayside magnetopause surface modes

Contact Info

Product

Resources

About