The Behavior of the Open Magnetic Field of the Sun

Fisk, L. A.; Schwadron, N. A.

doi:10.1086/322503

Cited by 208 publications

(220 citation statements)

References 31 publications

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“…We point out that the process sketched here leads to a transport of closed connections from equator to pole even as open solar flux is transported from the high latitudes to the equator (analogous to the complementarity of electron and hole transport in semiconductors); in real three-dimensional geometry this field may even be transported onto the opposite hemisphere. This likely has implications for the behavior of the heliospheric field (see Fisk & Schwadron 2001).…”

Section: Discussionmentioning

confidence: 99%

What Is Missing from Our Understanding of Long‐Term Solar and Heliospheric Activity?

Schrijver

DeRosa

Title

2002

ApJ

145

163

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The heliospheric magnetic field is associated with changes in space weather, cosmic-ray flux, and likely climate. This field is determined by the largest scale patterns of magnetism at the solar surface, dominated by the lower latitude active regions during cycle maximum and by the circumpolar fields during cycle minimum. Whereas the magnetic field in the activity belt is readily studied, the high-latitude field is much less accessible, and its study requires a combination of modeling and observation. Current models hold that the high-latitude magnetic field on the Sun is determined solely by the accumulation of field transported poleward from lower latitude active regions. We test this hypothesis by simulating the evolution of the magnetic field at the solar surface and in the heliosphere during the last 340 yr using a state-of-the-art model that incorporates all processes that are known to contribute significantly to the evolution of the large-scale patterns in the solar field. We find that if only the emergence frequency of magnetic bipoles is varied in accordance with observed sunspot records, the polar-cap field reservoir does not match measurements during past years. Based on comparisons of our simulations with observed polar fluxes over the last few decades and with the proxy for the heliospheric flux formed by 340 yr of 10 Be ice-core data, we suggest that the high-latitude field may be subject to decay on a timescale of 5-10 yr. We discuss the consequences of this finding for our understanding of the Sun-Earth connection and explore inferences for the coupling of the Sun's internal magnetic field to the heliospheric field.

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Section: Discussionmentioning

confidence: 99%

What Is Missing from Our Understanding of Long‐Term Solar and Heliospheric Activity?

Schrijver

DeRosa

Title

2002

ApJ

145

163

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“…Measuring this variable connection is essential to understanding how the solar corona changes over the solar cycle, how open flux is transferred into interplanetary space, and possibly how the corona is heated and the solar wind accelerated. These measurements would permit tests of the importance of interchange reconnection, a model that aims to jointly explain coronal This figure is an example of the pitch angle distribution for 272 eV electrons observed by ACE SWEPAM over one day illustrating BDEs and dropouts consistent with the spacecraft passing through closed and open field lines heating and solar wind formation by proposing that open magnetic field lines are present all over the Sun, including regions that are predominantly closed (Fisk and Schwadron 2001;Crooker et al 2002). Reconnection between an open field line and one end of a closed magnetic loop effectively causes the footpoint of the open line to jump discontinuously to the other end of the loop.…”

Section: Sources Of the Solar Windmentioning

confidence: 99%

Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe Plus

et al. 2015

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The Solar Wind Electrons Alphas and Protons (SWEAP) Investigation on SolarProbe Plus is a four sensor instrument suite that provides complete measurements of the electrons and ionized helium and hydrogen that constitute the bulk of solar wind and coronal plasma. SWEAP consists of the Solar Probe Cup (SPC) and the Solar Probe Analyzers (SPAN). SPC is a Faraday Cup that looks directly at the Sun and measures ion and electron fluxes and flow angles as a function of energy. SPAN consists of an ion and electron electrostatic analyzer (ESA) on the ram side of SPP (SPAN-A) and an electron ESA on the anti-ram side (SPAN-B). The SPAN-A ion ESA has a time of flight section that enables it to sort particles by their mass/charge ratio, permitting differentiation of ion species. SPAN-A and -B are rotated relative to one another so their broad fields of view combine like the seams on a baseball to view the entire sky except for the region obscured by the heat shield and covered by SPC. Observations by SPC and SPAN produce the combined field of view and measurement capabilities required to fulfill the science objectives of SWEAP and Solar Probe Plus. SWEAP measurements, in concert with magnetic and electric fields, energetic particles, and white light contextual imaging will enable discovery and understanding of solar wind acceleration and formation, coronal and solar wind heating, and particle acceleration in the inner heliosphere of the solar system. SPC and SPAN are managed by the SWEAP Electronics Module (SWEM), which distributes power, formats onboard data products, and serves as a single electrical interface to the spacecraft. SWEAP data products include ion and electron velocity distribution functions with high energy and angular resolution. Full resolution data are stored within the SWEM, enabling high resolution observations of structures such as shocks, reconnection events, and other transient structures to be selected for download after the fact. This paper describes the implementation of the SWEAP Investigation, the driving requirements for the suite, expected performance of the instruments, and planned data products, as of mission preliminary design review.

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“…CMEs drag additional magnetic flux into the heliosphere, and if left unabated would result in magnetic flux in the heliosphere that increases without bound (Gosling 1975;McComas 1995). Since this does not occur, it is believed that the magnetic field in the CME reconnects with the background open magnetic flux in a process that has been labeled interchange reconnection (Gosling et al 1995;Fisk & Schwadron 2001;Crooker et al 2002). The CME flux is then converted into open flux, with no net increases in the heliospheric magnetic field.…”

Section: The Behavior Of the Heliospheric Magnetic Field During The Smentioning

confidence: 99%

“…Over the last decade we have developed theories for the behavior of the heliospheric magnetic field (Fisk 1996;Zurbuchen et al 1997;Fisk et al 1999a,b;Fisk 1999;Fisk & Schwadron 2001;Fisk 2005;Fisk & Zurbuchen 2006), and for the acceleration of the solar wind (Fisk et al 1998Fisk 2003). During the current solar minimum, the heliospheric magnetic field and the solar wind are behaving in ways that are different from any previous minimum for which we have good spacecraft observations.…”

Section: Introductionmentioning

confidence: 99%

The heliospheric magnetic field and the solar wind during the solar cycle

Fisk

Zhao

2008

Proc. IAU

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Abstract. The heliospheric magnetic field and the solar wind are behaving differently in the current solar minimum, compared to the previous minimum. The radial component of the heliospheric magnetic field, and thus the average value of the component of the solar magnetic field that opens into the heliosphere, the so-called open magnetic flux of the Sun, is lower than it was in the previous solar minimum; in fact, lower than in any previous solar minimum for which there are good spacecraft observations. The mass flux, the ram pressure, and the coronal electron temperature as measured by solar wind charge states are also lower in the current minimum compared to the previous one. This situation provides an opportunity to test some of the concepts for the behavior of the heliospheric magnetic field and the solar wind that have been developed; to improve these theories, and to construct a theory for the solar wind that accounts for the observed behavior throughout the solar cycle, including the current unusual solar minimum.

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The Behavior of the Open Magnetic Field of the Sun

Cited by 208 publications

References 31 publications

What Is Missing from Our Understanding of Long‐Term Solar and Heliospheric Activity?

What Is Missing from Our Understanding of Long‐Term Solar and Heliospheric Activity?

Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe Plus

The heliospheric magnetic field and the solar wind during the solar cycle

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