Magnetostatic atmospheres in a spherical geometry and their application to the solar corona

Hundhausen, Joan R.; Hundhausen, A. J.; Zweibel, Ellen G.

doi:10.1029/ja086ia13p11117

Cited by 25 publications

(18 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The weaker response of the GCR intensity to changes in B at such times is attributed to the drift-induced preference for positively charged particles to approach the inner heliosphere from the poles at these times (Jokipii and Thomas 1981) and the relative confinement of CMEs to low latitudes at the onset of the solar (modulation) cycle (Hundhausen 1993;Gopalswamy et al 2010). As the cycle develops, CMEs form at progressively higher latitudes.…”

Section: Discussionmentioning

confidence: 99%

Solar Drivers of 11-yr and Long-Term Cosmic Ray Modulation

Cliver¹,

Richardson²,

Ling³

2011

Cosmic Rays in the Heliosphere

View full text Add to dashboard Cite

In the current paradigm for the modulation of galactic cosmic rays (GCRs), diffusion is taken to be the dominant process during solar maxima while drift dominates at minima. Observations during the recent solar minimum challenge the pre-eminence of drift: at such times. In 2009, the rv2 GV GCR intensity measured by the Newark neutron monitor increased by "'5% relative to its maximum value two cycles earlier even though the average tilt angle in 2009 was slightly larger than that in 1986 (--,-,20° vs. rv 14°), while solar wind B was significantly lower (rv 3.9 nT vs. "'5.4 nT). A decomposition of the solar wind into high-speed streams, slow solar wind, and coronal mass ejections (CMEs; including postshock flows) reveals that the Sun transmits its message of changing magnetic field (diffusion coefficient) to the heliosphere primarily through CMEs at solar maximum and high-speed streams at solar minimum. Long-term reconstructions of solar wind B are in general agreement for the rv 1900-present interval and can be used to reliably estimate GCR intensity over this period. For earlier epochs, however, a recent lOBe-based reconstruction covering the past"" 10 4 years shows nine abrupt and relatively short-lived drops of B to ;SO nT, with the first of these corresponding to the Sporer minimum. Such dips are at variance with the recent suggestion that B has a minimum or floor value of ""2.8 nT. A floor in solar wind B implies a ceiling in the GCR intensity (a permanent modulation of the local interstellar spectrum) at a given energy/rigidity. The 30-40% increase in the intensity of 2.5 GV electrons observed by Ulysses during the recent solar minimum raises an interesting paradox that will need to be resolved. E.W. Cliver (12Sl) Space Vehicles

show abstract

Section: Discussionmentioning

confidence: 99%

Solar Drivers of 11-yr and Long-Term Cosmic Ray Modulation

Cliver¹,

Richardson²,

Ling³

2011

Cosmic Rays in the Heliosphere

View full text Add to dashboard Cite

show abstract

“…allowing for the forces due to pressure and gravity in the usual notation (Hundhausen, Hundhausen, and Zweibel, 1981;Uchida and Low, 1982;Low and Smith, 1993). The expansion of the corona into the solar wind drags all magnetic fields beyond this region into the open configuration.…”

Section: The Quiescent Coronamentioning

confidence: 99%

Solar activity and the corona

1996

View full text Add to dashboard Cite

This review puts together what we have learned about coronal structures and phenomenology to synthesize a physical picture of the corona as a voluminous, thermally and electrically highly-conducting atmosphere responding dynamically to the injection of magnetic flux from below. The synthesis describes complementary roles played by the magnetic heating of the corona, the different types of flares, and the coronal mass ejections as physical processes by which magnetic flux and helicity make their way from below the photosphere into the corona, and, ultimately, into interplanetary space. In these processes, a physically meaningful interplay among dissipative magnetohydrodynamic turbulence, ideal ordered flows, and magnetic helicity determines how and when the rich variety of relatively long-lived coronal structures, spawned by the emerged magnetic flux, will evolve quasi-steadily or erupt with the impressive energies characteristic of flares and coronal mass ejections. Central to this picture is the suggestion, based on recent theoretical and observational works, that the the emerged flux may take the form of a twisted flux rope residing principally in the corona. Such a flux rope is identified with the low-density cavity at the base of a coronal helmet, often but not always encasing a quiescent prominence. The flux rope may either be bodily transported into the corona from below the photosphere, or reform out of a state of flaring turbulence under some suitable constraint of magnetic-helicity conservation. The appeal of this synthesis is its physical simplicity and the manner it relates a large set of diverse phenomena into a self-consistent whole. The implications of this view point are discussed.The topics covered are: the large-scale corona; helmet streamers; quiescent prominences; coronal mass ejections; flares and heating; magnetic reconnection and magnetic helicity; and, the hydromagnetics of magnetic flux emergence.

show abstract

“…It is a standard procedure to guess F (ψ) when modelling structures in the solar corona, e.g. prominences and arcades (Dungey 1953;Low 1980;Hundhausen, Hundhausen, & Zweibel 1981;Zweibel & Hundhausen 1982;Webb 1988;Sozou 1998), as well as accretion onto compact objects (Uchida & Low 1981;Hameury et al 1983;Brown & Bildsten 1998;Litwin et al 2001). Čadež, Oliver, & Ballester (1994) used an ad hoc pressure balance condition at a simple, fixed boundary to determine, rather than guess, F (ψ).…”

Section: Equations Of Hydromagnetic Force Balancementioning

confidence: 99%

Hydromagnetic Structure of a Neutron Star Accreting at Its Polar Caps

Melatos

Phinney

2001

Publ. – Astron. Soc. Aust

101

View full text Add to dashboard Cite

The hydromagnetic structure of a neutron star accreting symmetrically at both magnetic poles is calculated as a function of accreted mass, Ma, starting from a polytropic sphere plus central magnetic dipole (Ma =0) and evolving the configuration through a quasistatic sequence of twodimensional, Grad–Shafranov equilibria as Ma increases. It is found that the accreted material spreads equatorward under its own weight, compressing the magnetic field into a thin boundary layer and burying it everywhere except in a narrow, equatorial belt. The magnetic dipole moment of the star is given by µ=5.2×1024(B0/1012.5G)1.3(Ma/10−8Mʘ yr−1)0.18(Ma/Mʘ)−1.3Gcm3, and the fractional difference between its principal moments of inertia is given by Є=2.1×10−5(B0/1012.5G)0.27(Ma/10−8Myr−1)0.18(Ma/Mʘ)1.7, for Ma in the range 10−5Ma/Mʘ10−1,where B0 is the pre-accretion magnetic field strength, and Ma is the accretion rate.

show abstract

Magnetostatic atmospheres in a spherical geometry and their application to the solar corona

Cited by 25 publications

References 8 publications

Solar Drivers of 11-yr and Long-Term Cosmic Ray Modulation

Solar Drivers of 11-yr and Long-Term Cosmic Ray Modulation

Solar activity and the corona

Hydromagnetic Structure of a Neutron Star Accreting at Its Polar Caps

Contact Info

Product

Resources

About