Impact of CIRs/CMEs on the ionospheres of Venus and Mars

Niklas Edberg IRF Uppsala, Sweden

H. Nilsson, Y. Futaana,

G. Stenberg, D. Andrews,

K. Ågren, S. Barabash,

H. Opgenoorth, J.-E. Wahlund,

M. Lester, S. Cowley, University of Leicester, UK

J. Luhmann, T. McEnulty SSL Berkeley, USA

M. Fränz MPI, Germany

A. Fedorov CESR, France

T.L. Zhang Graz, Austria

EPSC, Madrid, 2012

Observations of CIRs at Mars Each major CIR observed by ACE at Earth can also

observed by MEX at Mars during 2007-2008

6 examples of CIRs in ACE and MEX data during 3 solar rotations.

ACE

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Superposed epoch analysis of 41 CIRs

ACE data Mars Express data|B|

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Atmospheric escape during CIR at Mars The amount of

outflowing heavy planetary ions increases by a factor of ~2.5 when a CIR passes by

~30% of the total outflow of heavy planetary ions occur during ~15% of the time, when pressure pulses impact.

Important implications for atmospheric evolution at Mars. Edberg et al., GRL,

2010

Observations of CIRs/CMEs at Venus CIRs/CMEs that are observed at ACE are also easily

tracked to Venus. From May 2006- Jan 2010 we find 147 events.

10 examples of CIRs in ACE and VEX data during 3 solar rotations.

Atmospheric escape during CIR at Venus

The amount of outflowing heavy planetary ions (O+) increases by a factor of ~1.9, on average over 147 CIRs/CMEs.

The escape rate increase can occasionally be significantly higher.

Edberg et al., JGR, 2011

Related work

Luhmann et al., 2007, showed that the flux of planetary ions from Venus can increase by a factor 100 when CMEs impact the planet.

McEnulty et al., 2010 showed that planetary ions from Venus are picked up and accelerated by the convective electric field to a greater extent when CMEs impact.

Related work

Dubinin et al., 2009, estimated that the atmospheric escape increased by a factor of ~10 when a CIR impacted on Mars due to the increased scavenging of the ionosphere.

Futaana et al., 2008, estimated that heavy ion outflow from Mars and Venus increased by a factor of ~5-10, and suggested that solar energetic particles might play a role.

The influence of dynamic pressure increase

The CIR events with the highest mean dynamic pressure show a 30% higher outflow rate than the low pressure events

The dynamic pressure is important!

The escape rate from Mars increased with increasing solar wind dynamic pressure [Lundin et al., 2008; Nilsson et al., 2010] and EUV flux [Lundin et al., 2008].

Another mechanism – magnetic reconnection during IMF rotations

Across each CIR the IMF changes polarity, and so will the induced magnetosphere of Venus (and Mars).

When anti-parallel magnetic fields from opposite sides of the CIRs meet magnetic reconnection events could be initiated on the dayside.

Ong et al., 1993, related ionospheric clouds to IMF rotations.

Similar to the comet-tail disconnection ideas by Brandt and Niedner, 1989.

Edberg et al., JGR, 2011

Zhang et al., 2012, Science

Dubinin, et al, 2012, GRL

More recent studies have revealed that magnetic reconnection is indeed occuring at Venus, at least in the tail region, as found by Zhang et al, 2012, and Dubinin et al., 2012.

Ionospheric escape from Titan• Alitude profiles from

the inbound passes of T55-T59.

• A high density region is observed farther and farther away during each pass, as the flyby geometry changes, indicating an escape plume in the tail region of Titan

• Ion composition measurements (prel.)confirm that the escaping ions in the tail are ionospheric (courtesy of Ronan Modolo)

• Ionospheric escape rates has recently been published by Coates et al., 2012

Edberg et al., PSS, 2011

Upstream variability at Titan

Morooka et al., 2009

Orbit of Titan Likely that Titan is behaving like Mars and Venus, and lose more plasma at a rate that is varying with upstream conditions.

Co-rotation flow

LP data from 85 Titan flybys

Summary

Venus loses 1.9 times more ionospheric plasma when CIRs or CMEs impact the planet.

Mars loses 2.5 times more ionospheric plasma when CIRs or CMEs impact the planet.

The increased escape is probably caused by a combination of increased Pdyn, increased pick up by Econv, increased solar energetic particle flux, magnetic reconnection during IMF rotations.

Titan might experience similar increased loss due to the varying plasma conditions in Saturn’s corotating plasma.

Calculate arrival time at Mars by taking into account the radial, ΔT1, and the longitudinal, ΔT2, time difference:

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ΔT = ΔT1 + ΔT2ΔT1 = r vSWΔT2 =Ω φSUN

ACE data|B|

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Calculate arrival time at Mars