Solar cycle variation of the heliospheric magnetic field Mathew Owens 10 September 2012

Overview Photospheric magnetic field (briefly) Ulysses Configuration of the heliospheric magnetic field R2 |BR| invariance Near-Earth observations Variation in total heliospheric flux Geomagnetic reconstructions Adding/removing heliospheric flux Suprathermal electron observations Relation to Solar Orbiter

Photospheric extrapolations Top: Riley et al, 2006 Bottom: Eclipse photograph, Carlos & Espenak, 1995. HMF observations are single-point measurements PFSS (etc.) provides invaluable global context BUT: Steady state (over 27 days) Minimum energy state of corona

Open Solar Flux (OSF) Unsigned Flux, FU=  |BR| r2 cos() dd Flux threading the coronal source surface Unsigned Flux, FU=  |BR| r2 cos() dd r = heliocentric distance BR = radial field  = solar latitude  = solar longitude +/2 2 -/2 0 “closed” field line “open” field lines

PFSS solutions Magnetic field polarity at coronal source surface

HCS location e.g., Smith el al., 2003

Ulysses e.g., McComas et al, 2003; Jones et al, 2002.

BR invariance |BR| ecliptic d R Earth Balogh et al., 1995; Smith et al., 2001; Lockwood et al., 2000 d |BR| ecliptic Earth R |BRE| Ulysses showed that everywhere |BR|(d/R)2 = |BRE| Thus total unsigned magnetic flux leaving the sun = 4R2 |BRE|

Heliospheric magnetic flux Owens et al., 2008

Total HMF

Geomagnetic reconstructions Svalgaard & Cliver, 2010; Lockwood & Owens, 2011

Note: Total HMF != OSF e.g., Wand & Sheeley, 1995; Lockwood and Owens, 2009; Erdos & Balogh 2012;

Suprathermal electrons e. g. , Feldman et al, 1975; Gosling et al Suprathermal electrons e.g., Feldman et al, 1975; Gosling et al., 1987; Crooker et al., 1998

Adding/removing OSF Solanki et al, 2000 OSF can be modelled as a continuity equation Source: New closed loops. Sunspots or CMEs Loss: Disconnection of magnetic flux. ??? Owens and Crooker, JGR, 2006 Owens and Crooker, JGR, 2007

Solar wind at 1 AU (Simple classification of ACE suprathermal electron data)

Closed HMF - new OSF e.g., Gosling et al, 1987; Low 2001

Closed HMF in magnetic clouds Shodhan et al,, 2002; Crooker et al, 2002; Crooker et al, 2008 1 AU 5 AU

OSF transport by CMEs Owens & Crooker, 2007 CMEs project the Hale cycle into the heliosphere Changes in PFSS solutions are associated with CME locations (e.g., Luhmann et al, 1998)

Inverted HMF – OSF removal

OSF loss and HCS tilt Owens et al, JGR, 2011

Solar Orbiter Close to Sun, combined remote and in situ observations, heliospheric imaging, etc. Quantify the relation between OSF and HMF measured at 1 AU (and beyond) Observe newly created and destroyed OSF before it evolves in transit to 1 AU What are the solar signatures of these processes? What fraction of the corona is undergoing these processes at any one time? Are there newly emerged loops in the absence of CMEs? How does this relate to the source of the slow solar wind.

PFSS - OMNI

PFSS -Ulysses

Ulysses Perihelion passes (Fast Latitude Scans)  1st - near sunspot min  2nd - near sunspot max

A rotating dipole?

Ulysses