Geomagnetic Activity Index Hpo

Yamazaki, Yosuke; Matzka, Jürgen; Stolle, Claudia; Kervalishvili, Guram; Rauberg, Jan; Bronkalla, Oliver; Morschhauser, A.; Bruinsma, Sean; Shprits, Y. Y.; Jackson, D. R.

doi:10.1029/2022gl098860

Cited by 42 publications

(35 citation statements)

References 37 publications

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“…Hourly values of the Dst index were used to evaluate storm effects on the geomagnetic field during the Hunga Tonga event. The geomagnetic activity index Hp30 (Yamazaki et al., 2022) was also used. Hp30 represents planetary geomagnetic activity in a similar way as the 3‐hourly geomagnetic activity index Kp (Matzka et al., 2021) but with a higher time resolution of 30 min.…”

Section: Datamentioning

confidence: 99%

Geomagnetic Detection of the Atmospheric Acoustic Resonance at 3.8 mHz During the Hunga Tonga Eruption Event on 15 January 2022

2022

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Geophysical events such as earthquakes, volcanoes and tsunamis can cause atmospheric waves such as acoustic waves and gravity waves (Yeh & Liu, 1974). Acoustic waves have frequencies higher than the acoustic cutoff frequency (∼3.2 mHz at the stratopause), while gravity waves have frequencies lower than the Brunt-Väisälä frequency (∼2.7 mHz at the stratopause). They can propagate away from the source, transferring energy and momentum into the middle and upper atmosphere. As the waves propagate to higher altitudes, they grow in amplitude due to decreasing atmospheric density. Yeh and Liu (1974) estimated that a seismic wave with vertical ground displacement of 5 mm could lead to an acoustic wave whose vertical wind velocity reaches 30 m/s at an altitude of 150 km. Such a large perturbation of the neutral atmosphere would have a significant impact on the dynamics and electrodynamics of the ionosphere. Indeed, ionospheric disturbances associated with acoustic and gravity waves have been reported following strong earthquakes and other geophysical events for many decades (see reviews by e.g., Astafyeva, 2019;Meng et al., 2019).Atmospheric oscillations with frequencies near the acoustic cutoff frequency are frequently observed after eruption events (Kanamori et al., 1994). Modeling studies have shown that those oscillations can be explained by acoustic waves trapped between the ground and thermosphere (e.g.

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Section: Datamentioning

confidence: 99%

Geomagnetic Detection of the Atmospheric Acoustic Resonance at 3.8 mHz During the Hunga Tonga Eruption Event on 15 January 2022

2022

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“…To quantify magnetic activity, we consider various indices with various time resolutions: Kp (3 hr time resolution) and the new geomagnetic indices Hpo, namely Hp60 (60 min time resolution) and Hp30 (30 min) (Yamazaki et al., 2022), together with AE (1 hr), SymH (1 hr), and Dst (1 hr). We also consider the hourly solar wind dynamic pressure, as well as, the solar wind speed (1 min time resolution) and the north‐south component of the interplanetary magnetic field (1 min).…”

Section: Methodsmentioning

confidence: 99%

Is Kp the Best Single Magnetic Activity Parameterization for Electromagnetic Radial Diffusion in the Outer Radiation Belt?

Fatmasiefa

Lejosne

2022

JGR Space Physics

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Specifying radial diffusion magnitude is one of the main requirements for most physics-based radiation belt models. Yet, radial diffusion quantification remains uncertain. The most commonly used parameterization for the logarithm of radial diffusion magnitude is a linear function of a magnetic index, 𝐴𝐴 Kp , with a coarse time resolution of 3 hours. This work presents alternate linear parameterizations of similar quality for the logarithm of radial diffusion magnitude, considering other magnetic indices and solar wind parameters. Using a publicly available time series for the logarithm of electromagnetic radial diffusion magnitude, we investigate linear relationships with magnetic indices such as Kp, Hp60, Hp30, AE, SymH, and Dst and solar wind parameters such as solar wind dynamic pressure, solar wind speed, and the north-south component of the interplanetary magnetic field. We find that Kp, Hp60, Hp30, and solar dynamical pressure yield the strongest linear correlation with the logarithm of radial diffusion magnitude. We also provide simple, energy-dependent, linear models of the logarithm of radial diffusion magnitude that best fit the time series, as well as quantifications of the root-mean square errors. This work contributes to improving the time resolution for radial diffusion parameterization and operational radiation belt models. In particular, it suggests that the new 30-min and 60-min geomagnetic indices Hpo (Hp30 and Hp60, respectively) could also be used in place of Kp in the most commonly used Kp-driven parameterizations for radiation belt radial diffusion, to improve the time resolution of the models. Plain Language SummaryThere is an increasing need to better understand and predict the near-Earth environment, especially the Van Allen radiation belts as there is an increasing number of spacecraft operating within these regions filled with high-energy charged particles. One option is to use physics-based computer codes to simulate these environments. One of the key inputs for these codes is radial diffusion magnitude, which quantifies the efficiency of the radial diffusion process that takes place within the radiation belts. Radial diffusion is commonly parameterized by one index called the 𝐴𝐴 Kp index to quantify how the process varies with magnetic activity. We question this choice, with the objective of improving radial diffusion models. We explore the behavior of radial diffusion magnitude when other simple ways to quantify magnetic activity are used in place of 𝐴𝐴 Kp . We provide alternate radial diffusion parameterization of similar quality and higher time resolution. The objective of this work is to contribute to current efforts in increasing the time resolution of radiation belt models.

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“…The top two plots show the HPF calibrated accelerations for both Swarm A and C, the third plot illustrates both the components of the PC index, whereas the bottom plot shows two geomagnetic indices, Hp60 and F10.7. The Hp60 is an open‐end hourly index recently introduced to express the global geomagnetic activity, especially during severe geomagnetic storms (Yamazaki et al., 2022). F10.7 is, instead, a daily index used to depict solar activity (SWPC & NOAA, 2022).…”

Section: Polar Featuresmentioning

confidence: 99%

Swarm A and C Accelerometers: Data Validation and Scientific Interpretation

Iorfida

Daras

Haagmans

et al. 2023

Earth and Space Science

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The fourth European Space Agency Earth Explorer (Swarm) was launched in 2013 and it comprises a constellation of three identical satellites. The primary mission objective is analyzing and modeling the geomagnetic field and its temporal evolution, based on the measurements of a vector and a scalar magnetometer on board. Each spacecraft (A, B, and C) carries an accelerometer, supposed to measure the non‐gravitational forces. However, this instrument did not work as expected; the processing of the related data sets has a significant latency. The focus was primarily on Swarm C, because its signal‐to‐noise ratio is the best amongst the three spacecrafts. For this satellite, the data are available for the whole mission timeline. At the end of 2021, a batch of Swarm A accelerometer data set was disseminated. Swarm A and C have flown side‐by‐side for most of the mission and, therefore, their measurements are supposed to be nearly identical after calibration. The work presented in this paper shows that such a correspondence occurs: at high frequency similar signatures are visible in both accelerometer data sets, near the equator and the poles. These features agree with measurements of other instruments on board and with earlier findings based on CHAllenging Minisatellite Payload and Gravity Recovery and Climate Experiment data. The equatorial structures show a correlation between the equatorial mass anomaly and the equatorial ionization anomaly. At the poles, the data are related to the polar cap index and to field‐aligned‐currents enhancements measured by the magnetometers on board. This research shows, for the first time, scientific results obtained from the Swarm accelerometers.

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Geomagnetic Activity Index Hpo

Cited by 42 publications

References 37 publications

Geomagnetic Detection of the Atmospheric Acoustic Resonance at 3.8 mHz During the Hunga Tonga Eruption Event on 15 January 2022

Geomagnetic Detection of the Atmospheric Acoustic Resonance at 3.8 mHz During the Hunga Tonga Eruption Event on 15 January 2022

Is Kp the Best Single Magnetic Activity Parameterization for Electromagnetic Radial Diffusion in the Outer Radiation Belt?

Swarm A and C Accelerometers: Data Validation and Scientific Interpretation

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