Correction to “Estimated errors in magnetic cloud model fit parameters with force‐free cylindrically symmetric assumptions”

Lepping, R. P.; Berdichevsky, D. B.; Ferguson, Timothy

doi:10.1029/2004ja010517

Cited by 9 publications

(23 citation statements)

References 2 publications

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“…These are the "Q 0 =1 set". Notice that χ R =0.165 corresponds to a MC field noise level v of 3.0 nT, according to Lepping et al (2003a;2004). The remaining cases within set 1,2, i.e.…”

Section: Appendix A: Criteria For Estimating Quality Of Magnetic Cloumentioning

confidence: 99%

“…This is described in a recent fit-parameter error study by Lepping et al (2003aLepping et al ( , 2004 and implemented in a related program that interpolates between the output parameter values developed in the original Lepping et al (1990) paper, to better enable its use. This error-interpolation program is given by the URL http://lepmfi.gsfc.nasa.gov/mfi/interpolation mc.pro.…”

Section: Error Estimations Of Magnetic Cloud Fit-parametersmentioning

confidence: 99%

See 1 more Smart Citation

A summary of WIND magnetic clouds for years 1995-2003: model-fitted parameters, associated errors and classifications

Lepping¹,

Berdichevsky²,

Wu³

et al. 2006

Ann. Geophys.

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189

267

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Abstract.Interplanetary magnetic clouds (MCs) have been identified for the first 8.6 years of the WIND mission, and their magnetic field structures have been parameter-fitted by a static, force free, cylindrically-symmetric model ) with various levels of success. This paper summarizes various aspects of the results of the model fitting by providing: seven estimated model fit-parameter values for each of the 82 MCs found, their objectively determined quality estimates, closest approach vectors (in two coordinate frames), fit-parameter errors for the cases of acceptable quality (50 cases, or 61%), axial magnetic fluxes, axial current densities, and total axial current -as well as some examples of MC profiles for various conditions and "categories" for each case (e.g. B z : N→S or S→N, etc.). MC quality is estimated from a quantitative consideration of a large set of parameters, such as the chi-squared of the model fit, degree of asymmetry of the B profile, and a comparison of two means of estimating radius. This set of MCs was initially identified by visual inspection of relevant field and plasma data. Each resulting MC candidate is then tested through the use of the MC parameter model, for various adjusted durations to determine the best fit, which helps to refine the boundarytimes. The resulting MC set is called Set 1. Another, larger, set (Set 2) of MCs is identified through an automated program whose criteria are based on general MC plasma and field characteristics at 1 AU determined through past experience. Set 1 is almost fully contained within Set 2, whose frequency of occurrence better matches that of the sunspot cycle than Set 1. The difference-set (Set 2-Set 1) is referred to as the magnetic cloud-like (MCL) set, whose members do not very well represent good flux ropes through modeling. We present a discussion of how a MC's front boundary isCorrespondence to: R. P. Lepping (ronald.p.lepping@nasa.gov) specifically identified in terms of multi-parameter considerations (i.e. any one or more of: increase in B, directional discontinuity, magnetic hole in B, drop in proton plasma beta, B-fluctuation level change, proton temperature drop, etc.), as well as through the application of the flux rope model. Also presented are examples of unusual MCs, as well as some commonly occurring relationships, such as the existence and frequency (approx. 1/2 the time) of upstream interplanetary shocks, and less frequent internal shocks.

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“…These are the "Q 0 =1 set". Notice that χ R =0.165 corresponds to a MC field noise level v of 3.0 nT, according to Lepping et al (2003a;2004). The remaining cases within set 1,2, i.e.…”

Section: Appendix A: Criteria For Estimating Quality Of Magnetic Cloumentioning

confidence: 99%

Section: Error Estimations Of Magnetic Cloud Fit-parametersmentioning

confidence: 99%

A summary of WIND magnetic clouds for years 1995-2003: model-fitted parameters, associated errors and classifications

Lepping¹,

Berdichevsky²,

Wu³

et al. 2006

Ann. Geophys.

Self Cite

189

267

View full text Add to dashboard Cite

show abstract

“…Otherwise we assume an uncertainty of ±20% in L L and L FC scaled from our uncertainty in the above estimate of L 0 . A detailed analysis of how the MC model parameters vary with magnetic field noise has been given by Lepping et al [2003].…”

Section: Magnetic Field Line Length Calculationsmentioning

confidence: 99%

“…We use two methods to calculate the MC field line lengths. First, we use the traditional Lundquist solution [Burlaga, 1995;Lepping et al, 2003Lepping et al, , 2006 for which the length L L of any field line from the Sun can be computed assuming a two-dimensional topology, characteristic of force-free flux ropes with no field components perpendicular to the rope axis. L L can be expressed in terms of the axial and tangential components of the MC magnetic field, which are orthogonal to each other:…”

Section: Magnetic Field Line Length Calculationsmentioning

confidence: 99%

Solar energetic electron probes of magnetic cloud field line lengths

2011

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[1] Magnetic clouds (MCs) are large interplanetary coronal mass ejections of enhanced and low-variance fields with rotations indicative of magnetic flux ropes originally connected to the Sun. The MC flux rope models require field lines with larger pitch angles and longer lengths with increasing distance from the MC axis. While the models can provide good fits to the in situ solar wind observations, there have not been definitive observational tests of the global magnetic field geometry, particularly for the field line lengths. However, impulsive solar energetic (E > 10 keV) electron events occasionally occur within an MC, and the electron onsets can be used to infer Le, the magnetic field line lengths traveled by the electrons from the Sun to the points in the MC where the electron onsets occur. We selected 8 MCs in and near which 30 solar electron events were observed by the 3DP instrument on the Wind spacecraft. We compared the corresponding Le values with calculated model field line lengths to test two MC models. Some limitations on the technique are imposed by variations of the models and uncertainly about MC boundary locations. We found generally poor correlations between the computed electron path lengths and the model field line lengths. Only one value of Le inside an MC, that of 18 October 1995, exceeded 3.2 AU, indicating an absence of the long path lengths expected in the highly wound outer regions of MC models. We briefly consider the implications for MC models.

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“…In particular, we analyze here the Lepping et al (1990) model's average ability to provide separately field directions and field magnitudes that are consistent with observations using a large number of WIND MCs. It is well know that this model is relatively good at reproducing the actual direction of the field for most events (and it generally provides good estimates of most of the model fit parameters, especially axial attitude, Lepping et al, 2003aLepping et al, , 2004, but its ability to capture the field magnitude profile across the MC is almost always poor. This is believed to be mainly due to the two oversimplifying assumptions that were employed in the model: (1) circular cross-section and (2) static nature of the MC (i.e., non-expanding).…”

Section: Introductionmentioning

confidence: 99%

Comparison of magnetic field observations of an average magnetic cloud with a simple force free model: the importance of field compression and expansion

Lepping

Narock

Chen³

2007

Ann. Geophys.

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Abstract.We investigate the ability of the cylindrically symmetric force-free magnetic cloud (MC) fitting model of Lepping et al. (1990) to faithfully reproduce actual magnetic field observations by examining two quantities: (1) a difference angle, called β, i.e., the angle between the direction of the observed magnetic field (B obs ) and the derived force free model field (B mod ) and (2) the difference in magnitudes between the observed and modeled fields, i.e., B(=|B obs |−|B mod |), and a normalized B (i.e., B/) is also examined, all for a judiciously chosen set of 50 WIND interplanetary MCs, based on quality considerations. These three quantities are developed as a percent of MC duration and averaged over this set of MCs to obtain average profiles. It is found that, although < B> and its normalize version are significantly enhanced (from a broad central average value) early in an average MC (and to a lesser extent also late in the MC), the angle <β> is small (less than 8 • ) and approximately constant all throughout the MC. The field intensity enhancements are due mainly to interaction of the MC with the surrounding solar wind plasma causing field compression at front and rear. For example, for a typical MC, B/ is: 0.21±0.27 very early in the MC, −0.11±0.10 at the center (and −0.085±0.12 averaged over the full "central region," i.e., for 30% to 80% of duration), and 0.05±0.29 very late in the MC, showing a double sign change as we travel from front to center to back, in the MC. When individual MCs are examined we find that over 80% of them possess field enhancements within several to many hours of the front boundary, but only about 30% show such enhancements at their rear portions. The enhancement of the MC's front field is also due to MC expansion, but this is usually a lesser effect compared to compression. It is expected that this compression is manifested as significant distortion to the MC's crosssection from the ideal circle, first suggested by Crooker et Correspondence to: R. P. Lepping (ronald.p.lepping@nasa.gov) al. (1990), into a more elliptical/oval shape, as some global MC studies seem to confirm (e.g., Riley and Crooker, 2004) and apparently also as confirmed for local studies of MCs (e.g., Hidalgo et al., 2002;Nieves-Chinchilla et al., 2005).

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Correction to “Estimated errors in magnetic cloud model fit parameters with force‐free cylindrically symmetric assumptions”

Cited by 9 publications

References 2 publications

A summary of WIND magnetic clouds for years 1995-2003: model-fitted parameters, associated errors and classifications

A summary of WIND magnetic clouds for years 1995-2003: model-fitted parameters, associated errors and classifications

Solar energetic electron probes of magnetic cloud field line lengths

Comparison of magnetic field observations of an average magnetic cloud with a simple force free model: the importance of field compression and expansion

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