Dynamics of the quiescent solar corona

Rosner, R.; Tucker, W.; Vaiana, G. S.

doi:10.1086/155949

Cited by 1,371 publications

(1,060 citation statements)

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“…The longitude of acceleration site gives a clue to predict the trajectories of accelerated particles for space weather usage, since the detection of particles is highly dependent on the magnetic connectivity from the foot point of the interplanetary (IP) magnetic field line to the spacecraft [e.g., Aschwanden, 2006]. Its height is also important, since the temperature and density of the corona change as the function of height [e.g., Rosner and Tucker, 1978]. In this study, we try to grasp the general circumstances of proton acceleration for the respective SPE groups in terms of their origins, acceleration mechanisms, and locations.…”

Section: 1002/2015ja021280mentioning

confidence: 99%

Characteristics of four SPE groups with different origins and acceleration processes

et al. 2015

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Solar proton events (SPEs) can be categorized into four groups based on their associations with flare or CME inferred from onset timings as well as acceleration patterns using multienergy observations. In this study, we have investigated whether there are any typical characteristics of associated events and acceleration sites in each group using 42 SPEs from 1997 to 2012. We find the following: (i) if the proton acceleration starts from a lower energy, a SPE has a higher chance to be a strong event (> 5000 particle flux per unit (pfu)) even if its associated flare and/or CME are not so strong. The only difference between the SPEs associated with flare and CME is the location of the acceleration site. (ii) For the former (Group A), the sites are very low (∼ 1 Rs) and close to the western limb, while the latter (Group C) have relatively higher (mean = 6.05 Rs) and wider acceleration sites. (iii) When the proton acceleration starts from the higher energy (Group B), a SPE tends to be a relatively weak event (< 1000 pfu), although its associated CME is relatively stronger than previous groups. (iv) The SPEs categorized by the simultaneous acceleration in whole energy range within 10 min (Group D) tend to show the weakest proton flux (mean = 327 pfu) in spite of strong associated eruptions. Based on those results, we suggest that the different characteristics of SPEs are mainly due to the different conditions of magnetic connectivity and particle density, which are changed with longitude and height as well as their origin.

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Section: 1002/2015ja021280mentioning

confidence: 99%

Characteristics of four SPE groups with different origins and acceleration processes

et al. 2015

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“…Individual loops detailed structure is highly variable in space and time and have been modeled by other authors using very strong simplifications (e.g. Rosner, Tucker, and Vaiana, 1978;Serio et al, 1981, also see review by Reale, 2010). Our models are focused on spectralirradiance synthesis and do not attempt to model individual active-region loops; instead the present models are intended to describe the SSI relevant properties of an ensemble of such loops, over the term of several hours, which is relevant to SSI and its effects on Earth's upper atmosphere.…”

Section: Structure Of the Low Coronamentioning

confidence: 99%

Far- and Extreme-UV Solar Spectral Irradiance and Radiance from Simplified Atmospheric Physical Models

et al. 2013

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This article describes an update of the physical models that we use to reconstruct the FUV and EUV irradiance spectra and the radiance spectra of the features that at any given point in time may cover the solar disk depending on the state of solar activity. The present update introduces important modifications to the chromosphere-corona transition region of all models. Also, the update introduces improved and extended atomic data. By these changes, the agreement of the computed and observed spectra is largely improved in many EUV lines important for the modeling of the Earth's upper atmosphere. This article describes the improvements and shows detailed comparisons with EUV/FUV radiance and irradiance measurements. The solar spectral irradiance from these models at wavelengths longer than ≈ 200 nm is discussed in a separate article.

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“…The corona is the outermost region of the solar atmosphere and is composed almost entirely of high-temperature [Rosner et al, 1978]. Some headway can be made without requiring the introduction of additional sources by adopting a value for the specific heat ratio near unity; however, a more realistic value for the specific heat ratio (i.e., q, -5/3) is needed if the effects of adiabatic cooling at larger heliocentric distances are to be correctly modeled.…”

Section: Physical Modelingmentioning

confidence: 99%

Global three‐dimensional MHD simulation of a space weather event: CME formation, interplanetary propagation, and interaction with the magnetosphere

Groth

Zeeuw²,

Gombosi³

et al. 2000

J. Geophys. Res.

262

255

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Abstract. A parallel adaptive mesh refinement (AMR) finite-volume scheme for predictingideal MHD flows is used to simulate the initiation, structure, and evolution of a coronal mass ejection (CME) and its interaction with the magnetosphere-ionosphere system. The simulated CME is driven by a local plasma density enhancement on the solar surface with the background initial state of the corona and solar wind represented by a newly devised "steady state" solution. The initial solution has been constructed to provide a reasonable description of the time-averaged solar wind for conditions near solar minimum: (1) the computed magnetic field near the Sun possesses high-latitude polar coronal holes, closed magnetic field flux tubes at low latitudes, and a helmet streamer structure with a neutral line and current sheet; (2) the Archimedean spiral topology of the interplanetary magnetic field is reproduced; (3) the observed two-state nature of the solar wind is also reproduced with the simulation yielding fast and slow solar wind streams at high and low latitudes, respectively; and (4) the predicted solar wind plasma properties at 1 AU are consistent with observations. Starting with the generation of a CME at the Sun, the simulation follows the evolution of the solar wind disturbance as it evolves into a magnetic cloud and travels through interplanetary space and subsequently interacts with the terrestrial magnetosphere-ionosphere system. The density-driven CME exhibits a two-step release process, with the front of the CME rapidly accelerating following the disruption of the near-Sun closed magnetic field line structure and then moving at a nearly constant speed of •560 km/s through interplanetary space. The CME also produces a large magnetic cloud (> 100/•s across) characterized by a magnetic field that smoothly rotates northward and then back again over a period of •2 days at 1 AU. The cloud does not contain a sustained period with a strong southward component of the magnetic field, and, as a consequence, the simulated CME is somewhat ineffective in generating strong geo-magnetic activity at Earth. Nevertheless, the simulation results illustrate the potential, as well as current limitations, of the MHD-based space weather model for enhancing the understanding of coronal physics, solar wind plasma processes, magnetospheric physics, and space weather phenomena. Such models will provide the foundation for future, more comprehensive space weather prediction tools.

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Dynamics of the quiescent solar corona

Cited by 1,371 publications

References 0 publications

Characteristics of four SPE groups with different origins and acceleration processes

Characteristics of four SPE groups with different origins and acceleration processes

Far- and Extreme-UV Solar Spectral Irradiance and Radiance from Simplified Atmospheric Physical Models

Global three‐dimensional MHD simulation of a space weather event: CME formation, interplanetary propagation, and interaction with the magnetosphere

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