**Author details**

with fixed radial distance *ρ* ¼ 0*:*54*λ*<sup>0</sup> and *vT* ¼ 0*:*2*CD* as can be seen in

values of *κe*,*<sup>i</sup>* ¼ 1*:*6 in the Lorentzian dusty plasma (**Figures 6** and **7**).

**4.5 Fast moving test charge response**

shielding around it in the Lorentzian dusty plasma.

to the Coulomb potential

*Selected Topics in Plasma Physics*

**5. Conclusion**

dusty plasma.

**Acknowledgements**

**102**

**Figure 7(a)** and **(b)**, respectively. It is important to examine that electron-to-ion temperature ratio suppresses the magnitudes of the WF and DH potentials at low

In this case, the test charge is assumed to be moving much faster than all the plasma species (viz., the electrons, ions and negatively charged dust grains). Consequently, Eq. (6) can be expressed in 1D form to finally arrive at *D k*ð Þ , **k***:***v***<sup>T</sup>* ≃1 in the limits *vT*∣ ≫ *ku <sup>j</sup>* and *ω* ¼ **k***:***v***T*. Thus, the test charge potential (7) simply leads

*<sup>ϕ</sup>*1ð Þ¼ **<sup>r</sup>**, *<sup>t</sup> <sup>ϕ</sup><sup>C</sup>* � *qT*

To conclude, we have briefly discussed different plasma diagnostic techniques and specifically investigated the novel features of interaction potentials caused by a test charge moving with constant velocity **v***<sup>T</sup>* along the z-axis in a collisionless unmagnetized Lorentzian dusty plasma. For this purpose, the linearized coupled Vlasov-Poisson equations are employed to model suprathermal electrons and ions with Kappa-df, as well as negatively charged dust grains with Maxwell-df, respectively. After applying the space-time Fourier transformations, an electrostatic potential is obtained with a modified dielectric constant. For taking the test charge speed much smaller than the dust thermal speed in a Lorentzian dusty plasma, we then express the total potential distribution in terms of short-range Debye-Hückel (DH) and long-range far-field potentials. The DH potential exponentially decays with distance, whereas FF potential decreases as the inverse cube of the distance. Both the potentials are substantially influenced by the plasma and superthermality parameters. However, a resonating test charge with DA oscillations introduces the long-range WF potential excitations behind the test charge in Lorentzian dusty plasmas. A Coulomb potential is obtained when the test charge is moving very fast compared to plasma species, and there is no shielding around it in the Lorentzian

Vladimirov and Nambu [40] have already utilized the idea of WF potential for making new materials by attracting the same polarity dust grains in dusty plasmas. The physics of attractive forces between the negatively charged dust grains is completely analogous to that of Cooper pairing of electrons in superconductors [59]. The dust particle physically polarizes the plasma medium and creates attractive potential regions, where positive ions from collective interaction of DA waves can be focused. This may in turn lead to the possibility for dust crystallization and

Dr. S. Ali dedicates this document to Late Prof. P.K. Shukla and Dr. B. Eliasson (University of Strathclyde, UK) who were very kind to him at many occasions

dust coagulation in both laboratory and space dusty plasmas.

It is now clear that if the test charge is moving very fast, then there is no

*<sup>r</sup> :* (16)

Shahid Ali1 \* and Yas Al-Hadeethi<sup>2</sup>

1 National Centre for Physics (NCP), Quaid-e-Azam University Campus, Islamabad, Pakistan

2 Faculty of Sciences, Department of Physics, King AbdulAziz University, Jeddah, Saudia Arabia

\*Address all correspondence to: shahid\_gc@yahoo.com

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
